Task 025: .AMG File Format
Task 025: .AMG File Format
Task Analysis and Response
The .AMG file extension is associated with multiple formats, but the provided web results suggest it is primarily linked to the AMGC Compressed Archive format, an obsolete format developed by Milen Georgiev for DOS, distributed as Turbo Pascal source code. Other potential associations include the AMG ACTOR System Image and SAMG Matrix Data, but these are less well-documented and also appear outdated. Additionally, there’s a reference to an Ambisonics sound file format, but this seems less likely to be the intended context given the programming task. Since no detailed specification for the AMGC Compressed Archive or other .AMG formats is publicly available, and the format is considered obsolete, I’ll proceed with the following assumptions based on the available information:
- AMGC Compressed Archive is a compressed file format, likely containing a header with metadata (e.g., file count, compression method, file sizes) and compressed data.
- Intrinsic properties to the file system would typically include metadata like file signature, version, compression method, file count, and offsets for archived files.
- Without a published specification, I’ll define a hypothetical but plausible structure for an AMGC Compressed Archive, as it’s the most referenced format. This structure will include common archive file properties to enable the required functionality.
If the user intended a different .AMG format (e.g., SAMG Matrix Data or Ambisonics), please clarify, and I can adjust the response. Below, I’ll address each task assuming the AMGC Compressed Archive format.
1. List of Properties of the .AMG File Format (AMGC Compressed Archive)
Based on typical archive file structures and the limited information available, the intrinsic properties of an AMGC Compressed Archive file likely include:
- File Signature: A unique identifier (e.g., "AMGC") to confirm the file type.
- Version: The format version (e.g., 1.0) for compatibility checks.
- Compression Method: An identifier for the compression algorithm used (e.g., 0 for none, 1 for RLE, etc.).
- File Count: The number of files stored in the archive.
- File Entries: A table of metadata for each archived file, including:
- File Name: Name of the archived file (string).
- File Size: Uncompressed size of the file (in bytes).
- Compressed Size: Size of the compressed data (in bytes).
- Offset: Position in the archive where the file’s compressed data begins.
- Data Section: The compressed data for all files, stored sequentially.
- Checksum: A value (e.g., CRC32) to verify archive integrity.
These properties are inferred based on common archive formats (e.g., ZIP, TAR) and the description of AMGC as a compressed archive utility.
2. Python Class for .AMG File Handling
Below is a Python class that opens, decodes, reads, writes, and prints the properties of a hypothetical .AMG (AMGC Compressed Archive) file. Since no compression algorithm is specified, I’ll assume a simple Run-Length Encoding (RLE) for demonstration, but the class can be extended for other methods.
import struct
import os
class AMGFile:
def __init__(self, filename, mode='r'):
self.filename = filename
self.mode = mode
self.signature = b'AMGC'
self.version = 1.0
self.compression_method = 1 # 1 for RLE
self.file_count = 0
self.entries = []
self.checksum = 0
self.file = None
if mode == 'r':
self.read()
elif mode == 'w':
self.file = open(filename, 'wb')
def read(self):
"""Read and decode an .AMG file."""
try:
with open(self.filename, 'rb') as f:
# Read header
signature = f.read(4)
if signature != self.signature:
raise ValueError("Invalid .AMG file signature")
self.version = struct.unpack('f', f.read(4))[0]
self.compression_method = struct.unpack('I', f.read(4))[0]
self.file_count = struct.unpack('I', f.read(4))[0]
self.checksum = struct.unpack('I', f.read(4))[0]
# Read file entries
for _ in range(self.file_count):
name_len = struct.unpack('I', f.read(4))[0]
name = f.read(name_len).decode('utf-8')
file_size, compressed_size, offset = struct.unpack('III', f.read(12))
self.entries.append({
'name': name,
'file_size': file_size,
'compressed_size': compressed_size,
'offset': offset
})
# Verify checksum (simplified)
f.seek(0)
calculated_checksum = sum(f.read()) & 0xFFFFFFFF
if calculated_checksum != self.checksum:
print("Warning: Checksum mismatch")
except Exception as e:
print(f"Error reading .AMG file: {e}")
def write(self, files):
"""Write files to a new .AMG archive."""
if self.mode != 'w':
raise ValueError("File not opened in write mode")
self.file_count = len(files)
self.entries = []
data_offset = 20 + sum(16 + len(name.encode('utf-8')) for name in files.keys()) # Header + entries
data = b''
# Prepare file entries and data
for name, content in files.items():
compressed = self._compress(content)
self.entries.append({
'name': name,
'file_size': len(content),
'compressed_size': len(compressed),
'offset': data_offset
})
data += compressed
data_offset += len(compressed)
# Write header
self.file.write(self.signature)
self.file.write(struct.pack('f', self.version))
self.file.write(struct.pack('I', self.compression_method))
self.file.write(struct.pack('I', self.file_count))
self.checksum = sum(self.signature + struct.pack('f', self.version) +
struct.pack('I', self.compression_method) +
struct.pack('I', self.file_count) + data) & 0xFFFFFFFF
self.file.write(struct.pack('I', self.checksum))
# Write file entries
for entry in self.entries:
name_bytes = entry['name'].encode('utf-8')
self.file.write(struct.pack('I', len(name_bytes)))
self.file.write(name_bytes)
self.file.write(struct.pack('III', entry['file_size'], entry['compressed_size'], entry['offset']))
# Write data
self.file.write(data)
self.file.flush()
def _compress(self, data):
"""Simple RLE compression (placeholder)."""
result = bytearray()
count = 1
last = data[0] if data else 0
for byte in data[1:]:
if byte == last and count < 255:
count += 1
else:
result.extend([last, count])
last = byte
count = 1
if data:
result.extend([last, count])
return bytes(result)
def _decompress(self, data, size):
"""Simple RLE decompression (placeholder)."""
result = bytearray()
for i in range(0, len(data), 2):
byte, count = data[i:i+2]
result.extend([byte] * count)
return bytes(result[:size])
def print_properties(self):
"""Print all intrinsic properties."""
print(f"File Signature: {self.signature.decode('utf-8')}")
print(f"Version: {self.version}")
print(f"Compression Method: {self.compression_method}")
print(f"File Count: {self.file_count}")
print("File Entries:")
for entry in self.entries:
print(f" Name: {entry['name']}")
print(f" File Size: {entry['file_size']} bytes")
print(f" Compressed Size: {entry['compressed_size']} bytes")
print(f" Offset: {entry['offset']}")
print(f"Checksum: {self.checksum}")
def close(self):
"""Close the file."""
if self.file:
self.file.close()
self.file = None
# Example usage
if __name__ == "__main__":
# Create an .AMG file
files = {
"test1.txt": b"Hello, World!",
"test2.txt": b"Another file content"
}
amg = AMGFile("test.amg", mode='w')
amg.write(files)
amg.print_properties()
amg.close()
# Read and print properties
amg = AMGFile("test.amg", mode='r')
amg.print_properties()
amg.close()
Explanation:
- The class assumes a file structure with a 20-byte header (4-byte signature, 4-byte version, 4-byte compression method, 4-byte file count, 4-byte checksum) followed by file entries and compressed data.
- RLE compression is used as a placeholder; in a real implementation, the actual compression method would need to be specified.
- The
print_propertiesmethod outputs all intrinsic properties. - Error handling ensures invalid files are detected (e.g., wrong signature or checksum).
3. Java Class for .AMG File Handling
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
public class AMGFile {
private String filename;
private String mode;
private String signature = "AMGC";
private float version = 1.0f;
private int compressionMethod = 1; // 1 for RLE
private int fileCount = 0;
private List<FileEntry> entries = new ArrayList<>();
private int checksum = 0;
private RandomAccessFile file;
static class FileEntry {
String name;
int fileSize;
int compressedSize;
int offset;
FileEntry(String name, int fileSize, int compressedSize, int offset) {
this.name = name;
this.fileSize = fileSize;
this.compressedSize = compressedSize;
this.offset = offset;
}
}
public AMGFile(String filename, String mode) throws IOException {
this.filename = filename;
this.mode = mode;
if (mode.equals("r")) {
file = new RandomAccessFile(filename, "r");
read();
} else if (mode.equals("w")) {
file = new RandomAccessFile(filename, "rw");
}
}
private void read() throws IOException {
byte[] sigBytes = new byte[4];
file.read(sigBytes);
if (!new String(sigBytes, StandardCharsets.UTF_8).equals(signature)) {
throw new IOException("Invalid .AMG file signature");
}
version = Float.intBitsToFloat(file.readInt());
compressionMethod = file.readInt();
fileCount = file.readInt();
checksum = file.readInt();
for (int i = 0; i < fileCount; i++) {
int nameLen = file.readInt();
byte[] nameBytes = new byte[nameLen];
file.read(nameBytes);
String name = new String(nameBytes, StandardCharsets.UTF_8);
int fileSize = file.readInt();
int compressedSize = file.readInt();
int offset = file.readInt();
entries.add(new FileEntry(name, fileSize, compressedSize, offset));
}
// Verify checksum (simplified)
file.seek(0);
byte[] content = new byte[(int) file.length()];
file.read(content);
int calculatedChecksum = 0;
for (byte b : content) {
calculatedChecksum += Byte.toUnsignedInt(b);
}
calculatedChecksum &= 0xFFFFFFFF;
if (calculatedChecksum != checksum) {
System.out.println("Warning: Checksum mismatch");
}
}
public void write(List<FileEntry> files, byte[][] contents) throws IOException {
if (!mode.equals("w")) {
throw new IOException("File not opened in write mode");
}
fileCount = files.size();
entries = files;
file.write(signature.getBytes(StandardCharsets.UTF_8));
file.writeInt(Float.floatToIntBits(version));
file.writeInt(compressionMethod);
file.writeInt(fileCount);
long dataOffset = 20 + files.stream().mapToLong(e -> 16 + e.name.length()).sum();
byte[] data = new byte[0];
for (int i = 0; i < files.size(); i++) {
FileEntry entry = files.get(i);
byte[] compressed = compress(contents[i]);
entry.compressedSize = compressed.length;
entry.offset = (int) dataOffset;
dataOffset += compressed.length;
data = concatenate(data, compressed);
}
checksum = calculateChecksum(data);
file.writeInt(checksum);
for (FileEntry entry : entries) {
byte[] nameBytes = entry.name.getBytes(StandardCharsets.UTF_8);
file.writeInt(nameBytes.length);
file.write(nameBytes);
file.writeInt(entry.fileSize);
file.writeInt(entry.compressedSize);
file.writeInt(entry.offset);
}
file.write(data);
}
private byte[] compress(byte[] data) {
// Placeholder RLE compression
ByteArrayOutputStream result = new ByteArrayOutputStream();
if (data.length == 0) return new byte[0];
int count = 1;
byte last = data[0];
for (int i = 1; i < data.length; i++) {
if (data[i] == last && count < 255) {
count++;
} else {
result.write(last);
result.write(count);
last = data[i];
count = 1;
}
}
result.write(last);
result.write(count);
return result.toByteArray();
}
private byte[] concatenate(byte[] a, byte[] b) {
byte[] result = new byte[a.length + b.length];
System.arraycopy(a, 0, result, 0, a.length);
System.arraycopy(b, 0, result, a.length, b.length);
return result;
}
private int calculateChecksum(byte[] data) {
int sum = 0;
for (byte b : signature.getBytes(StandardCharsets.UTF_8)) sum += Byte.toUnsignedInt(b);
for (byte b : data) sum += Byte.toUnsignedInt(b);
return sum & 0xFFFFFFFF;
}
public void printProperties() {
System.out.println("File Signature: " + signature);
System.out.println("Version: " + version);
System.out.println("Compression Method: " + compressionMethod);
System.out.println("File Count: " + fileCount);
System.out.println("File Entries:");
for (FileEntry entry : entries) {
System.out.println(" Name: " + entry.name);
System.out.println(" File Size: " + entry.fileSize + " bytes");
System.out.println(" Compressed Size: " + entry.compressedSize + " bytes");
System.out.println(" Offset: " + entry.offset);
}
System.out.println("Checksum: " + checksum);
}
public void close() throws IOException {
if (file != null) {
file.close();
}
}
public static void main(String[] args) throws IOException {
// Example usage
AMGFile amg = new AMGFile("test.amg", "w");
List<FileEntry> files = List.of(
new FileEntry("test1.txt", 13, 0, 0),
new FileEntry("test2.txt", 20, 0, 0)
);
byte[][] contents = {
"Hello, World!".getBytes(),
"Another file content".getBytes()
};
amg.write(files, contents);
amg.printProperties();
amg.close();
amg = new AMGFile("test.amg", "r");
amg.printProperties();
amg.close();
}
}
Explanation:
- Similar structure to the Python class, using
RandomAccessFilefor reading/writing. - Handles the same hypothetical file format with a header, file entries, and compressed data.
- RLE compression is a placeholder; replace with actual compression if known.
- Prints all properties as required.
4. JavaScript Class for .AMG File Handling
const fs = require('fs').promises;
const Buffer = require('buffer').Buffer;
class AMGFile {
constructor(filename, mode = 'r') {
this.filename = filename;
this.mode = mode;
this.signature = 'AMGC';
this.version = 1.0;
this.compressionMethod = 1; // 1 for RLE
this.fileCount = 0;
this.entries = [];
this.checksum = 0;
this.fileHandle = null;
}
async read() {
try {
const data = await fs.readFile(this.filename);
let offset = 0;
const sig = data.toString('utf8', 0, 4);
if (sig !== this.signature) {
throw new Error('Invalid .AMG file signature');
}
offset += 4;
this.version = data.readFloatLE(offset);
offset += 4;
this.compressionMethod = data.readUInt32LE(offset);
offset += 4;
this.fileCount = data.readUInt32LE(offset);
offset += 4;
this.checksum = data.readUInt32LE(offset);
offset += 4;
for (let i = 0; i < this.fileCount; i++) {
const nameLen = data.readUInt32LE(offset);
offset += 4;
const name = data.toString('utf8', offset, offset + nameLen);
offset += nameLen;
const fileSize = data.readUInt32LE(offset);
const compressedSize = data.readUInt32LE(offset + 4);
const fileOffset = data.readUInt32LE(offset + 8);
offset += 12;
this.entries.push({ name, fileSize, compressedSize, offset: fileOffset });
}
// Verify checksum (simplified)
let calculatedChecksum = 0;
for (const byte of data) {
calculatedChecksum += byte;
}
calculatedChecksum &= 0xFFFFFFFF;
if (calculatedChecksum !== this.checksum) {
console.warn('Warning: Checksum mismatch');
}
} catch (e) {
console.error(`Error reading .AMG file: ${e.message}`);
}
}
async write(files) {
if (this.mode !== 'w') {
throw new Error('File not opened in write mode');
}
this.fileCount = Object.keys(files).length;
this.entries = [];
let data = Buffer.alloc(0);
let dataOffset = 20 + Object.keys(files).reduce((sum, name) => sum + 16 + Buffer.from(name, 'utf8').length, 0);
for (const [name, content] of Object.entries(files)) {
const contentBuffer = Buffer.from(content);
const compressed = this.compress(contentBuffer);
this.entries.push({
name,
fileSize: contentBuffer.length,
compressedSize: compressed.length,
offset: dataOffset
});
dataOffset += compressed.length;
data = Buffer.concat([data, compressed]);
}
const buffer = Buffer.alloc(dataOffset);
let offset = 0;
buffer.write(this.signature, offset, 'utf8');
offset += 4;
buffer.writeFloatLE(this.version, offset);
offset += 4;
buffer.writeUInt32LE(this.compressionMethod, offset);
offset += 4;
buffer.writeUInt32LE(this.fileCount, offset);
offset += 4;
this.checksum = this.calculateChecksum(Buffer.concat([buffer.slice(0, offset), data]));
buffer.writeUInt32LE(this.checksum, offset);
offset += 4;
for (const entry of this.entries) {
const nameBytes = Buffer.from(entry.name, 'utf8');
buffer.writeUInt32LE(nameBytes.length, offset);
offset += 4;
nameBytes.copy(buffer, offset);
offset += nameBytes.length;
buffer.writeUInt32LE(entry.fileSize, offset);
buffer.writeUInt32LE(entry.compressedSize, offset + 4);
buffer.writeUInt32LE(entry.offset, offset + 8);
offset += 12;
}
buffer.write(data, offset);
await fs.writeFile(this.filename, buffer);
}
compress(data) {
// Placeholder RLE compression
const result = [];
if (!data.length) return Buffer.from([]);
let count = 1;
let last = data[0];
for (let i = 1; i < data.length; i++) {
if (data[i] === last && count < 255) {
count++;
} else {
result.push(last, count);
last = data[i];
count = 1;
}
}
result.push(last, count);
return Buffer.from(result);
}
calculateChecksum(data) {
let sum = 0;
for (const byte of data) {
sum += byte;
}
return sum & 0xFFFFFFFF;
}
printProperties() {
console.log(`File Signature: ${this.signature}`);
console.log(`Version: ${this.version}`);
console.log(`Compression Method: ${this.compressionMethod}`);
console.log(`File Count: ${this.fileCount}`);
console.log('File Entries:');
for (const entry of this.entries) {
console.log(` Name: ${entry.name}`);
console.log(` File Size: ${entry.fileSize} bytes`);
console.log(` Compressed Size: ${entry.compressedSize} bytes`);
console.log(` Offset: ${entry.offset}`);
}
console.log(`Checksum: ${this.checksum}`);
}
async close() {
this.fileHandle = null;
}
}
// Example usage
(async () => {
const amg = new AMGFile('test.amg', 'w');
await amg.write({
'test1.txt': 'Hello, World!',
'test2.txt': 'Another file content'
});
amg.printProperties();
await amg.close();
const amgRead = new AMGFile('test.amg', 'r');
await amgRead.read();
amgRead.printProperties();
await amgRead.close();
})();
Explanation:
- Uses Node.js
fsmodule for file operations. - Handles the same file structure with asynchronous read/write methods.
- RLE compression is a placeholder.
- Properties are printed to the console as required.
5. C Class for .AMG File Handling
Since C does not have classes, I’ll use a struct and functions to achieve the same functionality.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#define SIGNATURE "AMGC"
typedef struct {
char* name;
uint32_t file_size;
uint32_t compressed_size;
uint32_t offset;
} FileEntry;
typedef struct {
const char* filename;
char mode;
char signature[5];
float version;
uint32_t compression_method;
uint32_t file_count;
FileEntry* entries;
uint32_t checksum;
FILE* file;
} AMGFile;
AMGFile* amg_open(const char* filename, char mode) {
AMGFile* amg = (AMGFile*)malloc(sizeof(AMGFile));
strcpy(amg->signature, SIGNATURE);
amg->version = 1.0f;
amg->compression_method = 1; // RLE
amg->file_count = 0;
amg->entries = NULL;
amg->checksum = 0;
amg->filename = filename;
amg->mode = mode;
if (mode == 'r') {
amg->file = fopen(filename, "rb");
if (!amg->file) {
printf("Error: Cannot open file %s\n", filename);
free(amg);
return NULL;
}
amg_read(amg);
} else if (mode == 'w') {
amg->file = fopen(filename, "wb");
if (!amg->file) {
printf("Error: Cannot open file %s\n", filename);
free(amg);
return NULL;
}
}
return amg;
}
void amg_read(AMGFile* amg) {
char sig[5] = {0};
fread(sig, 1, 4, amg->file);
if (strcmp(sig, amg->signature) != 0) {
printf("Error: Invalid .AMG file signature\n");
return;
}
fread(&amg->version, sizeof(float), 1, amg->file);
fread(&amg->compression_method, sizeof(uint32_t), 1, amg->file);
fread(&amg->file_count, sizeof(uint32_t), 1, amg->file);
fread(&amg->checksum, sizeof(uint32_t), 1, amg->file);
amg->entries = (FileEntry*)malloc(amg->file_count * sizeof(FileEntry));
for (uint32_t i = 0; i < amg->file_count; i++) {
uint32_t name_len;
fread(&name_len, sizeof(uint32_t), 1, amg->file);
amg->entries[i].name = (char*)malloc(name_len + 1);
fread(amg->entries[i].name, 1, name_len, amg->file);
amg->entries[i].name[name_len] = '\0';
fread(&amg->entries[i].file_size, sizeof(uint32_t), 1, amg->file);
fread(&amg->entries[i].compressed_size, sizeof(uint32_t), 1, amg->file);
fread(&amg->entries[i].offset, sizeof(uint32_t), 1, amg->file);
}
// Verify checksum (simplified)
fseek(amg->file, 0, SEEK_SET);
uint32_t calc_checksum = 0;
int byte;
while ((byte = fgetc(amg->file)) != EOF) {
calc_checksum += byte;
}
calc_checksum &= 0xFFFFFFFF;
if (calc_checksum != amg->checksum) {
printf("Warning: Checksum mismatch\n");
}
}
void amg_write(AMGFile* amg, const char** names, const char** contents, uint32_t count) {
if (amg->mode != 'w') {
printf("Error: File not opened in write mode\n");
return;
}
amg->file_count = count;
amg->entries = (FileEntry*)malloc(count * sizeof(FileEntry));
uint32_t data_offset = 20 + count * 16;
for (uint32_t i = 0; i < count; i++) {
data_offset += strlen(names[i]);
}
// Prepare entries
uint32_t* compressed_sizes = (uint32_t*)malloc(count * sizeof(uint32_t));
uint8_t** compressed_data = (uint8_t**)malloc(count * sizeof(uint8_t*));
for (uint32_t i = 0; i < count; i++) {
size_t len = strlen(contents[i]);
compressed_data[i] = compress((uint8_t*)contents[i], len, &compressed_sizes[i]);
amg->entries[i].name = strdup(names[i]);
amg->entries[i].file_size = len;
amg->entries[i].compressed_size = compressed_sizes[i];
amg->entries[i].offset = data_offset;
data_offset += compressed_sizes[i];
}
// Write header
fwrite(amg->signature, 1, 4, amg->file);
fwrite(&amg->version, sizeof(float), 1, amg->file);
fwrite(&amg->compression_method, sizeof(uint32_t), 1, amg->file);
fwrite(&amg->file_count, sizeof(uint32_t), 1, amg->file);
// Calculate checksum
fseek(amg->file, 0, SEEK_SET);
uint32_t calc_checksum = 0;
int byte;
while ((byte = fgetc(amg->file)) != EOF) {
calc_checksum += byte;
}
for (uint32_t i = 0; i < count; i++) {
for (uint32_t j = 0; j < compressed_sizes[i]; j++) {
calc_checksum += compressed_data[i][j];
}
}
amg->checksum = calc_checksum & 0xFFFFFFFF;
fseek(amg->file, 16, SEEK_SET);
fwrite(&amg->checksum, sizeof(uint32_t), 1, amg->file);
// Write entries
for (uint32_t i = 0; i < count; i++) {
uint32_t name_len = strlen(amg->entries[i].name);
fwrite(&name_len, sizeof(uint32_t), 1, amg->file);
fwrite(amg->entries[i].name, 1, name_len, amg->file);
fwrite(&amg->entries[i].file_size, sizeof(uint32_t), 1, amg->file);
fwrite(&amg->entries[i].compressed_size, sizeof(uint32_t), 1, amg->file);
fwrite(&amg->entries[i].offset, sizeof(uint32_t), 1, amg->file);
}
// Write data
for (uint32_t i = 0; i < count; i++) {
fwrite(compressed_data[i], 1, compressed_sizes[i], amg->file);
free(compressed_data[i]);
}
free(compressed_sizes);
free(compressed_data);
}
uint8_t* compress(const uint8_t* data, size_t len, uint32_t* out_len) {
// Placeholder RLE compression
uint8_t* result = (uint8_t*)malloc(len * 2);
size_t pos = 0;
if (len == 0) {
*out_len = 0;
return result;
}
uint8_t last = data[0];
uint8_t count = 1;
for (size_t i = 1; i < len; i++) {
if (data[i] == last && count < 255) {
count++;
} else {
result[pos++] = last;
result[pos++] = count;
last = data[i];
count = 1;
}
}
result[pos++] = last;
result[pos++] = count;
*out_len = pos;
return result;
}
void amg_print_properties(AMGFile* amg) {
printf("File Signature: %s\n", amg->signature);
printf("Version: %.1f\n", amg->version);
printf("Compression Method: %u\n", amg->compression_method);
printf("File Count: %u\n", amg->file_count);
printf("File Entries:\n");
for (uint32_t i = 0; i < amg->file_count; i++) {
printf(" Name: %s\n", amg->entries[i].name);
printf(" File Size: %u bytes\n", amg->entries[i].file_size);
printf(" Compressed Size: %u bytes\n", amg->entries[i].compressed_size);
printf(" Offset: %u\n", amg->entries[i].offset);
}
printf("Checksum: %u\n", amg->checksum);
}
void amg_close(AMGFile* amg) {
if (amg->file) {
fclose(amg->file);
}
for (uint32_t i = 0; i < amg->file_count; i++) {
free(amg->entries[i].name);
}
free(amg->entries);
free(amg);
}
int main() {
AMGFile* amg = amg_open("test.amg", 'w');
const char* names[] = {"test1.txt", "test2.txt"};
const char* contents[] = {"Hello, World!", "Another file content"};
amg_write(amg, names, contents, 2);
amg_print_properties(amg);
amg_close(amg);
amg = amg_open("test.amg", 'r');
amg_print_properties(amg);
amg_close(amg);
return 0;
}
Explanation:
- Uses a
structto mimic a class, with functions for reading, writing, and printing. - Handles the same hypothetical file format with RLE compression as a placeholder.
- Memory management is explicit to prevent leaks.
- Prints all properties to the console.
Notes and Limitations
- Lack of Specification: The .AMG file format, particularly AMGC Compressed Archive, lacks a publicly available specification. The implementation assumes a typical archive structure with a header, file entries, and compressed data. If the user has access to the actual specification (e.g., Turbo Pascal source code from Milen Georgiev), please provide it for a precise implementation.
- Compression: RLE is used as a placeholder due to the unknown compression method. Real-world AMGC may use a custom algorithm, which would require reverse-engineering or documentation.
- Cross-Platform: The Python, Java, and JavaScript implementations are portable, but the C code assumes a standard file system. Adjust for platform-specific file handling if needed.
- Error Handling: All implementations include basic error handling (e.g., invalid signature, checksum mismatches), but additional robustness may be needed for production use.
- Alternative Formats: If the .AMG file is meant to be SAMG Matrix Data, AMG ACTOR System Image, or an Ambisonics sound file, the structure would differ significantly. Please confirm the exact format for a tailored solution.
If you have additional details about the .AMG format or a specific compression method, I can refine the implementations accordingly.
1. List of Properties of the .AMG File Format
The .AMG file format is a proposed extension of the WAVE-EX (WAV with extensible format) audio file format for Ambisonic G-Format audio. It stores pre-decoded Ambisonic soundfields as speaker feeds, with metadata to recover original B-Format channels. The format is based on the RIFF (Resource Interchange File Format) structure, consisting of chunks like 'fmt ', 'data', and the custom 'AMBG' chunk. All multi-byte integers are little-endian. The properties intrinsic to the file format (i.e., its structural elements, headers, fields, and metadata) are as follows:
RIFF Header:
- Signature: 4 bytes ('RIFF')
- File size: 4-byte unsigned integer (total size minus 8 bytes)
- Format type: 4 bytes ('WAVE')
fmt Chunk (WAVE_FORMAT_EXTENSIBLE):
- Chunk ID: 4 bytes ('fmt ')
- Chunk size: 4-byte unsigned integer (typically 40 for extensible)
- Format tag: 2-byte unsigned integer (0xFFFE for extensible)
- Number of channels (nChannels): 2-byte unsigned integer (number of speaker feeds, e.g., 4 for square, 5 for pentagon)
- Sample rate (nSamplesPerSec): 4-byte unsigned integer (e.g., 44100 Hz)
- Average bytes per second (nAvgBytesPerSec): 4-byte unsigned integer (sample rate * block align)
- Block align (nBlockAlign): 2-byte unsigned integer (channels * bits per sample / 8)
- Bits per sample (wBitsPerSample): 2-byte unsigned integer (e.g., 16, 24, 32)
- Extra size (cbSize): 2-byte unsigned integer (22 for extensible)
- Valid bits per sample (wValidBitsPerSample): 2-byte unsigned integer (matches or less than bits per sample)
- Channel mask (dwChannelMask): 4-byte unsigned integer (bitmask for speaker positions, e.g., 0xF for quad)
- Subformat GUID: 16 bytes (e.g., {00000001-0000-0010-8000-00AA00389B71} for PCM, {00000003-0000-0010-8000-00AA00389B71} for IEEE float)
AMBG Chunk (Ambisonic G-Format metadata):
- Chunk ID: 4 bytes ('AMBG')
- Chunk size (dataSize): 4-byte unsigned integer (size of data section excluding ID and size)
- Version: 4-byte unsigned integer (1 for the current specification)
- Number of B-Format channels (numBformat): 4-byte unsigned integer (≥3, e.g., 4 for first-order 3D)
- Decoder flags (decoderFlags): 4-byte unsigned integer (bitmask):
- Bit 0 (0x00000001): UHJ source (1 if source was two-channel UHJ)
- Bit 1 (0x00000002): Forward preference applied (relevant for UHJ)
- Bit 2 (0x00000004): Shelf filters applied
- Bit 3 (0x00000008): Speaker distance compensation applied
- Bit 4 (0x00000010): Dominance applied
- Bits 5-19: Reserved for future use
- B-Format conversion array (repeated numBformat times):
- Label: 4-byte unsigned integer (enum: 1=W, 2=X, 3=Y, 4=Z, 5=R, 6=S, 7=T, 8=U, 9=V, 10=K, 11=L, 12=M, 13=N, 14=O, 15=P, 16=Q)
- Coefficients: Array of 8-byte doubles (IEEE 754 64-bit floating point), length equal to nChannels from fmt chunk (weights for recovering each B-Format channel from speaker feeds)
data Chunk:
- Chunk ID: 4 bytes ('data')
- Chunk size: 4-byte unsigned integer (size of audio data)
- Audio data: Interleaved speaker feeds (format per fmt chunk, e.g., float or PCM samples)
Optional SPOS Chunk (Speaker Position, not required but recommended):
- Not intrinsic/mandatory, so excluded from core properties.
Other intrinsic properties include: little-endian byte order, support for PCM or floating-point audio, and the ability to recover B-Format via matrix multiplication using coefficients.
2. Python Class
import struct
import uuid
class AMGFile:
def __init__(self, filename):
self.filename = filename
self.properties = {}
self.audio_data = b''
self._parse()
def _parse(self):
with open(self.filename, 'rb') as f:
data = f.read()
offset = 0
# RIFF Header
riff, filesize, wave = struct.unpack_from('<4sI4s', data, offset)
if riff != b'RIFF' or wave != b'WAVE':
raise ValueError("Not a valid WAVE file")
self.properties['riff_signature'] = riff.decode()
self.properties['file_size'] = filesize
self.properties['wave_signature'] = wave.decode()
offset += 12
while offset < len(data):
chunk_id, chunk_size = struct.unpack_from('<4sI', data, offset)
offset += 8
chunk_data = data[offset:offset + chunk_size]
offset += chunk_size + (chunk_size % 2) # Pad to even
if chunk_id == b'fmt ':
(formattag, channels, samplerate, avgbytespersec, blockalign, bitspersample,
cbsize, validbits, channelmask) = struct.unpack('<HHIIHHHHI', chunk_data[:26])
subformat = uuid.UUID(bytes_le=chunk_data[26:42])
self.properties.update({
'format_tag': formattag,
'channels': channels,
'sample_rate': samplerate,
'avg_bytes_per_sec': avgbytespersec,
'block_align': blockalign,
'bits_per_sample': bitspersample,
'extra_size': cbsize,
'valid_bits_per_sample': validbits,
'channel_mask': channelmask,
'subformat_guid': str(subformat)
})
elif chunk_id == b'AMBG':
version, numbformat, decoderflags = struct.unpack('<III', chunk_data[:12])
self.properties.update({
'ambg_version': version,
'num_bformat': numbformat,
'decoder_flags': decoderflags,
'bformat_conversions': []
})
chunk_offset = 12
for _ in range(numbformat):
label = struct.unpack_from('<I', chunk_data, chunk_offset)[0]
chunk_offset += 4
coeffs = struct.unpack_from(f'<{self.properties["channels"]}d', chunk_data, chunk_offset)
chunk_offset += 8 * self.properties['channels']
self.properties['bformat_conversions'].append({
'label': label,
'coefficients': list(coeffs)
})
elif chunk_id == b'data':
self.audio_data = chunk_data
self.properties['data_size'] = chunk_size
def write(self, output_filename):
with open(output_filename, 'wb') as f:
# RIFF Header
riff_data = b''
riff_data += struct.pack('<4s4s', b'fmt ', 40)
riff_data += struct.pack('<HHIIHHHHI', self.properties['format_tag'], self.properties['channels'],
self.properties['sample_rate'], self.properties['avg_bytes_per_sec'],
self.properties['block_align'], self.properties['bits_per_sample'],
self.properties['extra_size'], self.properties['valid_bits_per_sample'],
self.properties['channel_mask'])
subformat_bytes = uuid.UUID(self.properties['subformat_guid']).bytes_le
riff_data += subformat_bytes + b'\x00\x00' # Padding for GUID if needed
# AMBG Chunk
ambg_data = struct.pack('<III', self.properties['ambg_version'], self.properties['num_bformat'],
self.properties['decoder_flags'])
for conv in self.properties['bformat_conversions']:
ambg_data += struct.pack('<I', conv['label'])
ambg_data += struct.pack(f'<{self.properties["channels"]}d', *conv['coefficients'])
ambg_chunk = struct.pack('<4sI', b'AMBG', len(ambg_data)) + ambg_data
# Data Chunk
data_chunk = struct.pack('<4sI', b'data', len(self.audio_data)) + self.audio_data
# Full RIFF
full_data = riff_data + ambg_chunk + data_chunk
f.write(struct.pack('<4sI4s', b'RIFF', len(full_data) + 4, b'WAVE') + full_data)
3. Java Class
import java.io.*;
import java.nio.*;
import java.util.*;
public class AMGFile {
private String filename;
private Map<String, Object> properties = new HashMap<>();
private byte[] audioData = new byte[0];
public AMGFile(String filename) {
this.filename = filename;
parse();
}
private void parse() {
try (RandomAccessFile raf = new RandomAccessFile(filename, "r")) {
ByteBuffer bb = ByteBuffer.allocate((int) raf.length()).order(ByteOrder.LITTLE_ENDIAN);
raf.getChannel().read(bb);
bb.rewind();
// RIFF Header
byte[] riff = new byte[4];
bb.get(riff);
int fileSize = bb.getInt();
byte[] wave = new byte[4];
bb.get(wave);
if (!new String(riff).equals("RIFF") || !new String(wave).equals("WAVE")) {
throw new IOException("Not a valid WAVE file");
}
properties.put("riff_signature", "RIFF");
properties.put("file_size", fileSize);
properties.put("wave_signature", "WAVE");
while (bb.hasRemaining()) {
byte[] chunkId = new byte[4];
bb.get(chunkId);
int chunkSize = bb.getInt();
ByteBuffer chunkBb = bb.slice().order(ByteOrder.LITTLE_ENDIAN);
bb.position(bb.position() + chunkSize + (chunkSize % 2));
if (new String(chunkId).equals("fmt ")) {
short formatTag = chunkBb.getShort();
short channels = chunkBb.getShort();
int sampleRate = chunkBb.getInt();
int avgBytesPerSec = chunkBb.getInt();
short blockAlign = chunkBb.getShort();
short bitsPerSample = chunkBb.getShort();
short cbSize = chunkBb.getShort();
short validBits = chunkBb.getShort();
int channelMask = chunkBb.getInt();
byte[] subformat = new byte[16];
chunkBb.get(subformat);
UUID subformatGuid = UUID.nameUUIDFromBytes(subformat); // Simplified
properties.put("format_tag", formatTag);
properties.put("channels", channels);
properties.put("sample_rate", sampleRate);
properties.put("avg_bytes_per_sec", avgBytesPerSec);
properties.put("block_align", blockAlign);
properties.put("bits_per_sample", bitsPerSample);
properties.put("extra_size", cbSize);
properties.put("valid_bits_per_sample", validBits);
properties.put("channel_mask", channelMask);
properties.put("subformat_guid", subformatGuid.toString());
} else if (new String(chunkId).equals("AMBG")) {
int version = chunkBb.getInt();
int numBformat = chunkBb.getInt();
int decoderFlags = chunkBb.getInt();
properties.put("ambg_version", version);
properties.put("num_bformat", numBformat);
properties.put("decoder_flags", decoderFlags);
List<Map<String, Object>> conversions = new ArrayList<>();
for (int i = 0; i < numBformat; i++) {
int label = chunkBb.getInt();
double[] coeffs = new double[(int) properties.get("channels")];
for (int j = 0; j < coeffs.length; j++) {
coeffs[j] = chunkBb.getDouble();
}
Map<String, Object> conv = new HashMap<>();
conv.put("label", label);
conv.put("coefficients", coeffs);
conversions.add(conv);
}
properties.put("bformat_conversions", conversions);
} else if (new String(chunkId).equals("data")) {
audioData = new byte[chunkSize];
chunkBb.get(audioData);
properties.put("data_size", chunkSize);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
public void write(String outputFilename) {
try (RandomAccessFile raf = new RandomAccessFile(outputFilename, "rw")) {
ByteBuffer bb = ByteBuffer.allocate(1024 * 1024).order(ByteOrder.LITTLE_ENDIAN); // Buffer, adjust size
// fmt Chunk
bb.put("fmt ".getBytes());
bb.putInt(40);
bb.putShort((short) properties.get("format_tag"));
bb.putShort((short) (int) properties.get("channels"));
bb.putInt((int) properties.get("sample_rate"));
bb.putInt((int) properties.get("avg_bytes_per_sec"));
bb.putShort((short) (int) properties.get("block_align"));
bb.putShort((short) (int) properties.get("bits_per_sample"));
bb.putShort((short) (int) properties.get("extra_size"));
bb.putShort((short) (int) properties.get("valid_bits_per_sample"));
bb.putInt((int) properties.get("channel_mask"));
// Subformat GUID - parse and put bytes
UUID guid = UUID.fromString((String) properties.get("subformat_guid"));
bb.putLong(guid.getMostSignificantBits());
bb.putLong(guid.getLeastSignificantBits());
// AMBG Chunk
List<Map<String, Object>> conversions = (List<Map<String, Object>>) properties.get("bformat_conversions");
ByteBuffer ambgBb = ByteBuffer.allocate(12 + conversions.size() * (4 + 8 * (int) properties.get("channels"))).order(ByteOrder.LITTLE_ENDIAN);
ambgBb.putInt((int) properties.get("ambg_version"));
ambgBb.putInt((int) properties.get("num_bformat"));
ambgBb.putInt((int) properties.get("decoder_flags"));
for (Map<String, Object> conv : conversions) {
ambgBb.putInt((int) conv.get("label"));
double[] coeffs = (double[]) conv.get("coefficients");
for (double coeff : coeffs) {
ambgBb.putDouble(coeff);
}
}
bb.put("AMBG".getBytes());
bb.putInt(ambgBb.capacity());
bb.put(ambgBb.array());
// data Chunk
bb.put("data".getBytes());
bb.putInt(audioData.length);
bb.put(audioData);
// RIFF Header
ByteBuffer fullBb = ByteBuffer.allocate(bb.position() + 12).order(ByteOrder.LITTLE_ENDIAN);
fullBb.put("RIFF".getBytes());
fullBb.putInt(bb.position() + 4);
fullBb.put("WAVE".getBytes());
fullBb.put(bb.flip().array(), 0, bb.limit());
raf.write(fullBb.array(), 0, fullBb.limit());
} catch (IOException e) {
e.printStackTrace();
}
}
}
4. JavaScript Class
const fs = require('fs');
const { Buffer } = require('buffer');
const { v4: uuidv4 } = require('uuid'); // For GUID handling, install uuid if needed
class AMGFile {
constructor(filename) {
this.filename = filename;
this.properties = {};
this.audioData = Buffer.alloc(0);
this.parse();
}
parse() {
const data = fs.readFileSync(this.filename);
let offset = 0;
// RIFF Header
const riff = data.slice(offset, offset + 4).toString();
offset += 4;
const fileSize = data.readUInt32LE(offset);
offset += 4;
const wave = data.slice(offset, offset + 4).toString();
offset += 4;
if (riff !== 'RIFF' || wave !== 'WAVE') {
throw new Error('Not a valid WAVE file');
}
this.properties.riff_signature = riff;
this.properties.file_size = fileSize;
this.properties.wave_signature = wave;
while (offset < data.length) {
const chunkId = data.slice(offset, offset + 4).toString();
offset += 4;
const chunkSize = data.readUInt32LE(offset);
offset += 4;
const chunkData = data.slice(offset, offset + chunkSize);
offset += chunkSize + (chunkSize % 2);
if (chunkId === 'fmt ') {
const formatTag = chunkData.readUInt16LE(0);
const channels = chunkData.readUInt16LE(2);
const sampleRate = chunkData.readUInt32LE(4);
const avgBytesPerSec = chunkData.readUInt32LE(8);
const blockAlign = chunkData.readUInt16LE(12);
const bitsPerSample = chunkData.readUInt16LE(14);
const cbSize = chunkData.readUInt16LE(16);
const validBits = chunkData.readUInt16LE(18);
const channelMask = chunkData.readUInt32LE(20);
const subformat = chunkData.slice(24, 40); // GUID bytes
this.properties.format_tag = formatTag;
this.properties.channels = channels;
this.properties.sample_rate = sampleRate;
this.properties.avg_bytes_per_sec = avgBytesPerSec;
this.properties.block_align = blockAlign;
this.properties.bits_per_sample = bitsPerSample;
this.properties.extra_size = cbSize;
this.properties.valid_bits_per_sample = validBits;
this.properties.channel_mask = channelMask;
this.properties.subformat_guid = subformat.toString('hex'); // Simplified
} else if (chunkId === 'AMBG') {
const version = chunkData.readUInt32LE(0);
const numBformat = chunkData.readUInt32LE(4);
const decoderFlags = chunkData.readUInt32LE(8);
this.properties.ambg_version = version;
this.properties.num_bformat = numBformat;
this.properties.decoder_flags = decoderFlags;
this.properties.bformat_conversions = [];
let chunkOffset = 12;
for (let i = 0; i < numBformat; i++) {
const label = chunkData.readUInt32LE(chunkOffset);
chunkOffset += 4;
const coeffs = [];
for (let j = 0; j < this.properties.channels; j++) {
coeffs.push(chunkData.readDoubleLE(chunkOffset));
chunkOffset += 8;
}
this.properties.bformat_conversions.push({ label, coefficients: coeffs });
}
} else if (chunkId === 'data') {
this.audioData = chunkData;
this.properties.data_size = chunkSize;
}
}
}
write(outputFilename) {
let buffers = [];
// fmt Chunk
const fmtBuffer = Buffer.alloc(48);
fmtBuffer.write('fmt ', 0, 4);
fmtBuffer.writeUInt32LE(40, 4);
fmtBuffer.writeUInt16LE(this.properties.format_tag, 8);
fmtBuffer.writeUInt16LE(this.properties.channels, 10);
fmtBuffer.writeUInt32LE(this.properties.sample_rate, 12);
fmtBuffer.writeUInt32LE(this.properties.avg_bytes_per_sec, 16);
fmtBuffer.writeUInt16LE(this.properties.block_align, 20);
fmtBuffer.writeUInt16LE(this.properties.bits_per_sample, 22);
fmtBuffer.writeUInt16LE(this.properties.extra_size, 24);
fmtBuffer.writeUInt16LE(this.properties.valid_bits_per_sample, 26);
fmtBuffer.writeUInt32LE(this.properties.channel_mask, 28);
// Subformat - assume hex string, convert back to buffer
const subformatBuf = Buffer.from(this.properties.subformat_guid, 'hex');
subformatBuf.copy(fmtBuffer, 32);
buffers.push(fmtBuffer);
// AMBG Chunk
let ambgSize = 12;
this.properties.bformat_conversions.forEach(conv => {
ambgSize += 4 + 8 * this.properties.channels;
});
const ambgBuffer = Buffer.alloc(8 + ambgSize);
ambgBuffer.write('AMBG', 0, 4);
ambgBuffer.writeUInt32LE(ambgSize, 4);
ambgBuffer.writeUInt32LE(this.properties.ambg_version, 8);
ambgBuffer.writeUInt32LE(this.properties.num_bformat, 12);
ambgBuffer.writeUInt32LE(this.properties.decoder_flags, 16);
let ambgOffset = 20;
this.properties.bformat_conversions.forEach(conv => {
ambgBuffer.writeUInt32LE(conv.label, ambgOffset);
ambgOffset += 4;
conv.coefficients.forEach(coeff => {
ambgBuffer.writeDoubleLE(coeff, ambgOffset);
ambgOffset += 8;
});
});
buffers.push(ambgBuffer);
// data Chunk
const dataBuffer = Buffer.alloc(8 + this.audioData.length);
dataBuffer.write('data', 0, 4);
dataBuffer.writeUInt32LE(this.audioData.length, 4);
this.audioData.copy(dataBuffer, 8);
buffers.push(dataBuffer);
// RIFF Header
const fullLength = buffers.reduce((acc, buf) => acc + buf.length, 4); // +4 for WAVE
const riffBuffer = Buffer.alloc(12);
riffBuffer.write('RIFF', 0, 4);
riffBuffer.writeUInt32LE(fullLength, 4);
riffBuffer.write('WAVE', 8, 4);
const fullBuffer = Buffer.concat([riffBuffer, ...buffers]);
fs.writeFileSync(outputFilename, fullBuffer);
}
}
5. C++ Class
#include <fstream>
#include <vector>
#include <string>
#include <cstring>
#include <cstdint>
#include <iostream>
#include <uuid/uuid.h> // May need external lib for UUID
struct BFormatConversion {
uint32_t label;
std::vector<double> coefficients;
};
class AMGFile {
private:
std::string filename;
// Properties
std::string riff_signature;
uint32_t file_size;
std::string wave_signature;
uint16_t format_tag;
uint16_t channels;
uint32_t sample_rate;
uint32_t avg_bytes_per_sec;
uint16_t block_align;
uint16_t bits_per_sample;
uint16_t extra_size;
uint16_t valid_bits_per_sample;
uint32_t channel_mask;
std::string subformat_guid; // As string
uint32_t ambg_version;
uint32_t num_bformat;
uint32_t decoder_flags;
std::vector<BFormatConversion> bformat_conversions;
uint32_t data_size;
std::vector<char> audio_data;
public:
AMGFile(const std::string& fname) : filename(fname) {
parse();
}
void parse() {
std::ifstream file(filename, std::ios::binary | std::ios::ate);
size_t size = file.tellg();
file.seekg(0);
std::vector<char> data(size);
file.read(data.data(), size);
size_t offset = 0;
// RIFF Header
char riff[5] = {};
memcpy(riff, data.data() + offset, 4);
offset += 4;
memcpy(&file_size, data.data() + offset, 4);
offset += 4;
char wave[5] = {};
memcpy(wave, data.data() + offset, 4);
offset += 4;
if (std::string(riff) != "RIFF" || std::string(wave) != "WAVE") {
throw std::runtime_error("Not a valid WAVE file");
}
riff_signature = riff;
wave_signature = wave;
while (offset < size) {
char chunk_id[5] = {};
memcpy(chunk_id, data.data() + offset, 4);
offset += 4;
uint32_t chunk_size;
memcpy(&chunk_size, data.data() + offset, 4);
offset += 4;
std::vector<char> chunk_data(chunk_size);
memcpy(chunk_data.data(), data.data() + offset, chunk_size);
offset += chunk_size + (chunk_size % 2);
if (std::string(chunk_id) == "fmt ") {
memcpy(&format_tag, chunk_data.data(), 2);
memcpy(&channels, chunk_data.data() + 2, 2);
memcpy(&sample_rate, chunk_data.data() + 4, 4);
memcpy(&avg_bytes_per_sec, chunk_data.data() + 8, 4);
memcpy(&block_align, chunk_data.data() + 12, 2);
memcpy(&bits_per_sample, chunk_data.data() + 14, 2);
memcpy(&extra_size, chunk_data.data() + 16, 2);
memcpy(&valid_bits_per_sample, chunk_data.data() + 18, 2);
memcpy(&channel_mask, chunk_data.data() + 20, 4);
char guid_bytes[16];
memcpy(guid_bytes, chunk_data.data() + 24, 16);
// Convert to string, simplified
char guid_str[37];
uuid_unparse((unsigned char*)guid_bytes, guid_str);
subformat_guid = guid_str;
} else if (std::string(chunk_id) == "AMBG") {
memcpy(&ambg_version, chunk_data.data(), 4);
memcpy(&num_bformat, chunk_data.data() + 4, 4);
memcpy(&decoder_flags, chunk_data.data() + 8, 4);
size_t chunk_offset = 12;
for (uint32_t i = 0; i < num_bformat; ++i) {
BFormatConversion conv;
memcpy(&conv.label, chunk_data.data() + chunk_offset, 4);
chunk_offset += 4;
conv.coefficients.resize(channels);
memcpy(conv.coefficients.data(), chunk_data.data() + chunk_offset, 8 * channels);
chunk_offset += 8 * channels;
bformat_conversions.push_back(conv);
}
} else if (std::string(chunk_id) == "data") {
data_size = chunk_size;
audio_data = chunk_data;
}
}
}
void write(const std::string& output_filename) {
std::ofstream file(output_filename, std::ios::binary);
// fmt Chunk
std::vector<char> fmt_chunk(48, 0);
memcpy(fmt_chunk.data(), "fmt ", 4);
uint32_t fmt_size = 40;
memcpy(fmt_chunk.data() + 4, &fmt_size, 4);
memcpy(fmt_chunk.data() + 8, &format_tag, 2);
memcpy(fmt_chunk.data() + 10, &channels, 2);
memcpy(fmt_chunk.data() + 12, &sample_rate, 4);
memcpy(fmt_chunk.data() + 16, &avg_bytes_per_sec, 4);
memcpy(fmt_chunk.data() + 20, &block_align, 2);
memcpy(fmt_chunk.data() + 22, &bits_per_sample, 2);
memcpy(fmt_chunk.data() + 24, &extra_size, 2);
memcpy(fmt_chunk.data() + 26, &valid_bits_per_sample, 2);
memcpy(fmt_chunk.data() + 28, &channel_mask, 4);
// GUID from string, simplified parse
uuid_t guid;
uuid_parse(subformat_guid.c_str(), guid);
memcpy(fmt_chunk.data() + 32, guid, 16);
// AMBG Chunk
size_t ambg_data_size = 12 + bformat_conversions.size() * (4 + 8 * channels);
std::vector<char> ambg_chunk(8 + ambg_data_size, 0);
memcpy(ambg_chunk.data(), "AMBG", 4);
memcpy(ambg_chunk.data() + 4, &ambg_data_size, 4);
memcpy(ambg_chunk.data() + 8, &ambg_version, 4);
memcpy(ambg_chunk.data() + 12, &num_bformat, 4);
memcpy(ambg_chunk.data() + 16, &decoder_flags, 4);
size_t ambg_offset = 20;
for (const auto& conv : bformat_conversions) {
memcpy(ambg_chunk.data() + ambg_offset, &conv.label, 4);
ambg_offset += 4;
memcpy(ambg_chunk.data() + ambg_offset, conv.coefficients.data(), 8 * channels);
ambg_offset += 8 * channels;
}
// data Chunk
std::vector<char> data_chunk(8 + audio_data.size());
memcpy(data_chunk.data(), "data", 4);
memcpy(data_chunk.data() + 4, &data_size, 4);
memcpy(data_chunk.data() + 8, audio_data.data(), data_size);
// RIFF Header
uint32_t full_size = fmt_chunk.size() + ambg_chunk.size() + data_chunk.size() + 4; // + WAVE
std::vector<char> riff_header(12, 0);
memcpy(riff_header.data(), "RIFF", 4);
memcpy(riff_header.data() + 4, &full_size, 4);
memcpy(riff_header.data() + 8, "WAVE", 4);
file.write(riff_header.data(), riff_header.size());
file.write(fmt_chunk.data(), fmt_chunk.size());
file.write(ambg_chunk.data(), ambg_chunk.size());
file.write(data_chunk.data(), data_chunk.size());
}
};