Task 009: .A File Format
Task 009: .A File Format
After reviewing the provided information and conducting a thorough analysis, I must note that there is no widely recognized or standardized ".A" file format with publicly available specifications in the context of common file systems or programming environments. The ".A" extension is ambiguous and could refer to various formats depending on the application, such as an archive file, a library file (e.g., static library in Unix-like systems), or a custom format specific to a niche program. However, based on the available data and common usage, the most likely candidate for a ".A" file in a programming context is a static library file (often used in Unix-like systems), which is an archive format typically managed by tools like ar.
Since no explicit ".A" file format specification was found in the provided references or general knowledge, I will assume the ".A" file refers to a Unix static library archive (commonly created with the ar tool), as this is a well-known use of the ".A" extension in programming. These files are essentially containers for object files, with a defined structure including a header and file entries. Below, I will:
- List the intrinsic properties of the Unix static library (.A) file format.
- Provide implementations in Python, Java, JavaScript, and C to open, read, write, and print the properties of such files.
If you meant a different ".A" file format (e.g., a custom format or something specific to your project), please provide additional details about the format, and I can tailor the response accordingly.
1. Properties of the .A File Format (Unix Static Library Archive)
The Unix static library archive (.A) is a container format created by the ar tool, used to bundle object files (e.g., .o files) into a single file for linking during compilation. Its intrinsic properties, based on the standard ar archive format, include:
- File Signature (Magic Number): A fixed 8-byte string
!<arch>\n(ASCII: 0x21 0x3C 0x61 0x72 0x63 0x68 0x3E 0x0A) that identifies the file as anararchive. - File Header: Each file within the archive has a 60-byte header containing:
- File Identifier: A 16-byte field (padded with spaces) specifying the name of the file or symbol table (e.g.,
/for the symbol table). - Timestamp: A 12-byte field (ASCII decimal) indicating the file's modification time.
- Owner ID: A 6-byte field (ASCII decimal) for the owner's user ID.
- Group ID: A 6-byte field (ASCII decimal) for the owner's group ID.
- File Mode: A 8-byte field (ASCII octal) specifying permissions (e.g.,
100644). - File Size: A 10-byte field (ASCII decimal) indicating the size of the file content in bytes.
- End Characters: A 2-byte field (
\x60\x0A, ASCII for "`\n") marking the end of the header. - Symbol Table (Optional): A special entry (named
/or//) containing a table of symbols for linking, often present in library archives. - File Contents: The actual data of each archived file (e.g., object code), following its header.
- Alignment: File contents are aligned to even-byte boundaries, with padding (newline characters, 0x0A) if necessary.
- File System Integration: The archive is stored as a single file in the file system, with no inherent compression or encryption unless applied externally.
These properties are intrinsic to the file's structure and how it is managed within the file system. Below, I implement classes in Python, Java, JavaScript, and C to handle these files, focusing on reading and writing the archive structure and printing the listed properties.
2. Python Class for .A File Format
import struct
import os
class AFileHandler:
def __init__(self, filepath):
self.filepath = filepath
self.magic = b'!<arch>\n'
self.header_format = '16s12s6s6s8s10s2s' # AR header format
def read_properties(self):
"""Read and print properties of the .A file."""
try:
with open(self.filepath, 'rb') as f:
# Check magic number
magic = f.read(8)
if magic != self.magic:
raise ValueError("Not a valid .A (ar) file")
print(f"File: {self.filepath}")
print(f"Magic Number: {magic.decode('ascii')}")
# Read headers and contents
while True:
header_data = f.read(60)
if not header_data:
break # End of file
if len(header_data) != 60:
raise ValueError("Incomplete header")
# Unpack header
identifier, timestamp, owner, group, mode, size, end = struct.unpack(self.header_format, header_data)
identifier = identifier.decode('ascii').rstrip()
timestamp = int(timestamp.decode('ascii').rstrip())
owner = int(owner.decode('ascii').rstrip())
group = int(group.decode('ascii').rstrip())
mode = int(mode.decode('ascii').rstrip(), 8)
size = int(size.decode('ascii').rstrip())
end = end.decode('ascii')
print("\nFile Entry:")
print(f" Identifier: {identifier}")
print(f" Timestamp: {timestamp}")
print(f" Owner ID: {owner}")
print(f" Group ID: {group}")
print(f" File Mode: {oct(mode)}")
print(f" File Size: {size} bytes")
print(f" End Characters: {end}")
# Read file content
content = f.read(size)
if len(content) != size:
raise ValueError("Incomplete file content")
# Align to even boundary
if size % 2 != 0:
f.read(1) # Skip padding byte
except Exception as e:
print(f"Error reading file: {e}")
def write_file(self, output_path, entries):
"""Write a new .A file with given entries (list of (identifier, content) tuples)."""
try:
with open(output_path, 'wb') as f:
# Write magic number
f.write(self.magic)
for identifier, content in entries:
if len(identifier) > 16:
raise ValueError("Identifier too long")
identifier = identifier.ljust(16).encode('ascii')
timestamp = str(int(os.time())).ljust(12).encode('ascii')
owner = b'0'.ljust(6)
group = b'0'.ljust(6)
mode = b'100644'.ljust(8)
size = str(len(content)).ljust(10).encode('ascii')
end = b'`\n'
# Write header
header = struct.pack(self.header_format, identifier, timestamp, owner, group, mode, size, end)
f.write(header)
# Write content
f.write(content)
# Add padding if needed
if len(content) % 2 != 0:
f.write(b'\n')
except Exception as e:
print(f"Error writing file: {e}")
# Example usage
if __name__ == "__main__":
# Example reading
handler = AFileHandler("example.a")
handler.read_properties()
# Example writing
entries = [("file1.o", b"Sample object file content"), ("file2.o", b"Another object file")]
handler.write_file("new.a", entries)
Explanation: This Python class uses the struct module to parse the fixed-length fields of the ar archive header. It reads the magic number, iterates through file entries, decodes their headers, and prints properties. The write_file method creates a new .A file with specified entries, ensuring proper formatting and padding.
3. Java Class for .A File Format
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.time.Instant;
public class AFileHandler {
private final String filepath;
private static final byte[] MAGIC = "!<arch>\n".getBytes(StandardCharsets.US_ASCII);
public AFileHandler(String filepath) {
this.filepath = filepath;
}
public void readProperties() {
try (RandomAccessFile file = new RandomAccessFile(filepath, "r")) {
// Check magic number
byte[] magic = new byte[8];
file.readFully(magic);
if (!new String(magic, StandardCharsets.US_ASCII).equals(new String(MAGIC, StandardCharsets.US_ASCII))) {
throw new IOException("Not a valid .A (ar) file");
}
System.out.println("File: " + filepath);
System.out.println("Magic Number: " + new String(magic, StandardCharsets.US_ASCII));
// Read headers and contents
while (file.getFilePointer() < file.length()) {
byte[] header = new byte[60];
file.readFully(header);
String identifier = new String(header, 0, 16, StandardCharsets.US_ASCII).trim();
long timestamp = Long.parseLong(new String(header, 16, 12, StandardCharsets.US_ASCII).trim());
int owner = Integer.parseInt(new String(header, 28, 6, StandardCharsets.US_ASCII).trim());
int group = Integer.parseInt(new String(header, 34, 6, StandardCharsets.US_ASCII).trim());
int mode = Integer.parseInt(new String(header, 40, 8, StandardCharsets.US_ASCII).trim(), 8);
long size = Long.parseLong(new String(header, 48, 10, StandardCharsets.US_ASCII).trim());
String end = new String(header, 58, 2, StandardCharsets.US_ASCII);
System.out.println("\nFile Entry:");
System.out.println(" Identifier: " + identifier);
System.out.println(" Timestamp: " + timestamp);
System.out.println(" Owner ID: " + owner);
System.out.println(" Group ID: " + group);
System.out.println(" File Mode: " + Integer.toOctalString(mode));
System.out.println(" File Size: " + size + " bytes");
System.out.println(" End Characters: " + end);
// Read file content
byte[] content = new byte[(int) size];
file.readFully(content);
// Align to even boundary
if (size % 2 != 0) {
file.readByte();
}
}
} catch (Exception e) {
System.err.println("Error reading file: " + e.getMessage());
}
}
public void writeFile(String outputPath, String[][] entries) {
try (RandomAccessFile file = new RandomAccessFile(outputPath, "rw")) {
// Write magic number
file.write(MAGIC);
for (String[] entry : entries) {
String identifier = entry[0];
byte[] content = entry[1].getBytes(StandardCharsets.US_ASCII);
if (identifier.length() > 16) {
throw new IOException("Identifier too long");
}
byte[] header = new byte[60];
System.arraycopy(identifier.getBytes(StandardCharsets.US_ASCII), 0, header, 0, identifier.length());
for (int i = identifier.length(); i < 16; i++) header[i] = ' ';
String timestamp = String.format("%-12d", Instant.now().getEpochSecond());
System.arraycopy(timestamp.getBytes(StandardCharsets.US_ASCII), 0, header, 16, 12);
String owner = "0".concat(" ".repeat(5));
System.arraycopy(owner.getBytes(StandardCharsets.US_ASCII), 0, header, 28, 6);
String group = "0".concat(" ".repeat(5));
System.arraycopy(group.getBytes(StandardCharsets.US_ASCII), 0, header, 34, 6);
String mode = "100644".concat(" ".repeat(2));
System.arraycopy(mode.getBytes(StandardCharsets.US_ASCII), 0, header, 40, 8);
String size = String.format("%-10d", content.length);
System.arraycopy(size.getBytes(StandardCharsets.US_ASCII), 0, header, 48, 10);
System.arraycopy("`\n".getBytes(StandardCharsets.US_ASCII), 0, header, 58, 2);
// Write header and content
file.write(header);
file.write(content);
// Add padding if needed
if (content.length % 2 != 0) {
file.write('\n');
}
}
} catch (Exception e) {
System.err.println("Error writing file: " + e.getMessage());
}
}
public static void main(String[] args) {
// Example reading
AFileHandler handler = new AFileHandler("example.a");
handler.readProperties();
// Example writing
String[][] entries = {{"file1.o", "Sample object file content"}, {"file2.o", "Another object file"}};
handler.writeFile("new.a", entries);
}
}
Explanation: The Java class uses RandomAccessFile for binary I/O, parsing the 60-byte headers and extracting properties. It handles the magic number, file entries, and alignment, with a method to write new archives.
4. JavaScript Class for .A File Format
const fs = require('fs').promises;
class AFileHandler {
constructor(filepath) {
this.filepath = filepath;
this.magic = Buffer.from('!<arch>\n');
}
async readProperties() {
try {
const file = await fs.open(this.filepath, 'r');
const buffer = Buffer.alloc(8);
await file.read(buffer, 0, 8, 0);
// Check magic number
if (!buffer.equals(this.magic)) {
throw new Error('Not a valid .A (ar) file');
}
console.log(`File: ${this.filepath}`);
console.log(`Magic Number: ${buffer.toString('ascii')}`);
let offset = 8;
while (true) {
const header = Buffer.alloc(60);
const { bytesRead } = await file.read(header, 0, 60, offset);
if (bytesRead === 0) break;
if (bytesRead !== 60) throw new Error('Incomplete header');
const identifier = header.slice(0, 16).toString('ascii').trim();
const timestamp = parseInt(header.slice(16, 28).toString('ascii').trim());
const owner = parseInt(header.slice(28, 34).toString('ascii').trim());
const group = parseInt(header.slice(34, 40).toString('ascii').trim());
const mode = parseInt(header.slice(40, 48).toString('ascii').trim(), 8);
const size = parseInt(header.slice(48, 58).toString('ascii').trim());
const end = header.slice(58, 60).toString('ascii');
console.log('\nFile Entry:');
console.log(` Identifier: ${identifier}`);
console.log(` Timestamp: ${timestamp}`);
console.log(` Owner ID: ${owner}`);
console.log(` Group ID: ${group}`);
console.log(` File Mode: ${mode.toString(8)}`);
console.log(` File Size: ${size} bytes`);
console.log(` End Characters: ${end}`);
// Read content
const content = Buffer.alloc(size);
await file.read(content, 0, size, offset + 60);
offset += 60 + size;
// Align to even boundary
if (size % 2 !== 0) {
await file.read(Buffer.alloc(1), 0, 1, offset);
offset += 1;
}
}
await file.close();
} catch (e) {
console.error(`Error reading file: ${e.message}`);
}
}
async writeFile(outputPath, entries) {
try {
const file = await fs.open(outputPath, 'w');
await file.write(this.magic);
for (const [identifier, content] of entries) {
if (identifier.length > 16) throw new Error('Identifier too long');
const header = Buffer.alloc(60);
header.write(identifier.padEnd(16), 0, 16, 'ascii');
header.write(String(Date.now() / 1000 | 0).padEnd(12), 16, 28, 'ascii');
header.write('0'.padEnd(6), 28, 34, 'ascii');
header.write('0'.padEnd(6), 34, 40, 'ascii');
header.write('100644'.padEnd(8), 40, 48, 'ascii');
header.write(String(content.length).padEnd(10), 48, 58, 'ascii');
header.write('`\n', 58, 60, 'ascii');
await file.write(header);
await file.write(content);
if (content.length % 2 !== 0) {
await file.write(Buffer.from('\n'));
}
}
await file.close();
} catch (e) {
console.error(`Error writing file: ${e.message}`);
}
}
}
// Example usage
(async () => {
const handler = new AFileHandler('example.a');
await handler.readProperties();
const entries = [
['file1.o', Buffer.from('Sample object file content')],
['file2.o', Buffer.from('Another object file')]
];
await handler.writeFile('new.a', entries);
})();
Explanation: This JavaScript class uses Node.js's fs.promises for asynchronous file operations. It reads the archive, parses headers, and prints properties, handling alignment. The writeFile method creates new archives with proper formatting.
5. C Class for .A File Format
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#define MAGIC "!<arch>\n"
#define HEADER_SIZE 60
typedef struct {
char filepath[256];
} AFileHandler;
void init_a_file_handler(AFileHandler* handler, const char* filepath) {
strncpy(handler->filepath, filepath, sizeof(handler->filepath) - 1);
}
void read_properties(AFileHandler* handler) {
FILE* file = fopen(handler->filepath, "rb");
if (!file) {
fprintf(stderr, "Error opening file: %s\n", handler->filepath);
return;
}
// Check magic number
char magic[8];
if (fread(magic, 1, 8, file) != 8 || strncmp(magic, MAGIC, 8) != 0) {
fprintf(stderr, "Not a valid .A (ar) file\n");
fclose(file);
return;
}
printf("File: %s\n", handler->filepath);
printf("Magic Number: %.8s\n", magic);
// Read headers and contents
char header[HEADER_SIZE];
while (fread(header, 1, HEADER_SIZE, file) == HEADER_SIZE) {
char identifier[17] = {0};
char timestamp[13] = {0};
char owner[7] = {0};
char group[7] = {0};
char mode[9] = {0};
char size[11] = {0};
char end[3] = {0};
strncpy(identifier, header, 16);
strncpy(timestamp, header + 16, 12);
strncpy(owner, header + 28, 6);
strncpy(group, header + 34, 6);
strncpy(mode, header + 40, 8);
strncpy(size, header + 48, 10);
strncpy(end, header + 58, 2);
long file_size = atol(size);
printf("\nFile Entry:\n");
printf(" Identifier: %s\n", identifier);
printf(" Timestamp: %ld\n", atol(timestamp));
printf(" Owner ID: %d\n", atoi(owner));
printf(" Group ID: %d\n", atoi(group));
printf(" File Mode: %o\n", (unsigned int)strtol(mode, NULL, 8));
printf(" File Size: %ld bytes\n", file_size);
printf(" End Characters: %s\n", end);
// Read content
char* content = malloc(file_size);
if (!content || fread(content, 1, file_size, file) != file_size) {
fprintf(stderr, "Error reading content\n");
free(content);
break;
}
free(content);
// Align to even boundary
if (file_size % 2 != 0) {
fseek(file, 1, SEEK_CUR);
}
}
fclose(file);
}
void write_file(AFileHandler* handler, const char* output_path, const char* entries[][2], int entry_count) {
FILE* file = fopen(output_path, "wb");
if (!file) {
fprintf(stderr, "Error opening output file: %s\n", output_path);
return;
}
// Write magic number
fwrite(MAGIC, 1, 8, file);
for (int i = 0; i < entry_count; i++) {
const char* identifier = entries[i][0];
const char* content = entries[i][1];
size_t content_len = strlen(content);
if (strlen(identifier) > 16) {
fprintf(stderr, "Identifier too long\n");
fclose(file);
return;
}
char header[HEADER_SIZE] = {0};
snprintf(header, 17, "%-16s", identifier);
snprintf(header + 16, 13, "%-12ld", (long)time(NULL));
snprintf(header + 28, 7, "%-6d", 0);
snprintf(header + 34, 7, "%-6d", 0);
snprintf(header + 40, 9, "%-8s", "100644");
snprintf(header + 48, 11, "%-10lu", (unsigned long)content_len);
snprintf(header + 58, 3, "`\n");
// Write header and content
fwrite(header, 1, HEADER_SIZE, file);
fwrite(content, 1, content_len, file);
if (content_len % 2 != 0) {
fwrite("\n", 1, 1, file);
}
}
fclose(file);
}
int main() {
AFileHandler handler;
init_a_file_handler(&handler, "example.a");
read_properties(&handler);
const char* entries[][2] = {
{"file1.o", "Sample object file content"},
{"file2.o", "Another object file"}
};
write_file(&handler, "new.a", entries, 2);
return 0;
}
Explanation: The C implementation uses standard I/O functions to read and write the archive. It parses headers, extracts properties, and handles alignment. The write_file function creates a new archive with specified entries.
Notes and Assumptions
- Assumption: The ".A" file format is assumed to be a Unix static library archive due to the lack of a specific ".A" format in the provided references and common usage in programming contexts.
- Handling: Each class handles reading (parsing headers and printing properties), writing (creating new archives), and alignment (ensuring even-byte boundaries).
- Error Handling: All implementations include basic error checking for file access, invalid formats, and incomplete data.
- Limitations: The implementations assume simple archives without extended features like long filenames (using
//entries) or complex symbol tables, as these are less common and not fully specified in the prompt. - Testing: The example usage in each class assumes a file
example.afor reading and createsnew.afor writing. You would need an actual .A file to test reading, or you can use the write functionality to create one.
If you have a specific ".A" file format in mind (e.g., a custom format or one used by a particular application), please provide its specifications or context, and I can revise the classes to match. Additionally, if you need clarification on any part of the implementation or want to focus on a specific language or feature, let me know!
File Format Specifications for .A
The .A file extension refers to static library archives in Unix-like systems, using the "ar" (archive) file format. This format is not formally standardized but has a common base with variants (e.g., GNU, BSD, System V). The most widely used is the GNU variant on Linux and similar platforms. The format consists of a global header (magic string) followed by member files, each with a fixed-size ASCII header containing metadata properties, followed by the member data (padded to even bytes if needed).
Based on reliable sources (e.g., ar.h header definitions and common variant descriptions), the format supports:
- Global magic: 8-byte ASCII string
!<arch>\n. - Per-member header: 60-byte ASCII structure with space-padded fields.
- Member data: Binary content, size as specified, with optional
\npadding for even alignment (not counted in size). - Special handling: For long filenames (>15 chars), a string table member named
//(GNU) or special name encoding (BSD). Symbol tables may be present as special members like/or/SYM64/. For this task, I'll focus on the common GNU-compatible variant with short names, as it's intrinsic and sufficient for basic .A files. Properties are stored in decimal (except mode in octal) as printable ASCII.
1. List of Properties Intrinsic to the File Format
These are the metadata properties stored in each member's header, analogous to file system inode attributes (name, timestamps, ownership, permissions, size). They are "intrinsic" as they define the archived file's identity and attributes within the archive structure:
- Name: The filename of the archived member (up to 15 characters; longer names use offsets to a string table in advanced variants).
- Modification Time: The file's last modification timestamp (seconds since Unix epoch, 1970-01-01).
- User ID (UID): The owning user's numeric ID.
- Group ID (GID): The owning group's numeric ID.
- Mode: The file permissions (Unix octal mode, e.g., 0644).
- Size: The size of the member's data in bytes (excluding any padding).
2. Python Class
import os
import struct
class AFileHandler:
MAGIC = b'!<arch>\n'
HEADER_FMT = '16s12s6s6s8s10s2s' # Struct format for header fields
HEADER_SIZE = 60
def __init__(self, filepath):
self.filepath = filepath
self.members = [] # List of dicts with properties and data
def read(self):
with open(self.filepath, 'rb') as f:
magic = f.read(8)
if magic != self.MAGIC:
raise ValueError("Not a valid .A file")
while True:
header = f.read(self.HEADER_SIZE)
if not header:
break
# Unpack header (all fields are ASCII, space-padded)
name, date, uid, gid, mode, size, fmag = struct.unpack(self.HEADER_FMT, header)
# Decode and strip padding/terminators
properties = {
'name': name.decode('ascii').rstrip(' /').strip(),
'modification_time': int(date.decode('ascii').strip()),
'uid': int(uid.decode('ascii').strip()),
'gid': int(gid.decode('ascii').strip()),
'mode': int(mode.decode('ascii').strip(), 8), # Octal
'size': int(size.decode('ascii').strip())
}
# Check terminator
if fmag != b'`\n':
raise ValueError("Invalid header terminator")
# Read data, handle padding
data = f.read(properties['size'])
if properties['size'] % 2 != 0:
padding = f.read(1)
if padding != b'\n':
raise ValueError("Invalid padding")
self.members.append({'properties': properties, 'data': data})
def write(self, output_path=None):
if not output_path:
output_path = self.filepath
with open(output_path, 'wb') as f:
f.write(self.MAGIC)
for member in self.members:
props = member['properties']
# Encode fields with padding
name = props['name'].ljust(16, ' ').encode('ascii')[:16]
date = str(props['modification_time']).rjust(12, ' ').encode('ascii')
uid = str(props['uid']).rjust(6, ' ').encode('ascii')
gid = str(props['gid']).rjust(6, ' ').encode('ascii')
mode = oct(props['mode'])[2:].rjust(8, ' ').encode('ascii')
size = str(props['size']).rjust(10, ' ').encode('ascii')
fmag = b'`\n'
header = name + date + uid + gid + mode + size + fmag
f.write(header)
f.write(member['data'])
if props['size'] % 2 != 0:
f.write(b'\n')
def add_member(self, name, data, modification_time, uid=0, gid=0, mode=0o644):
size = len(data)
properties = {
'name': name[:15], # Truncate for simplicity
'modification_time': modification_time,
'uid': uid,
'gid': gid,
'mode': mode,
'size': size
}
self.members.append({'properties': properties, 'data': data})
Usage example: handler = AFileHandler('example.a'); handler.read(); handler.write('new.a'). This handles basic short-name members; extend for long names/symbol tables if needed.
3. Java Class
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
public class AFileHandler {
private static final byte[] MAGIC = "!<arch>\n".getBytes(StandardCharsets.US_ASCII);
private static final int HEADER_SIZE = 60;
private static final byte[] FMAG = {'`', '\n'};
private String filepath;
private List<Member> members = new ArrayList<>();
static class Member {
String name;
long modificationTime;
int uid;
int gid;
int mode;
long size;
byte[] data;
}
public AFileHandler(String filepath) {
this.filepath = filepath;
}
public void read() throws IOException {
try (RandomAccessFile raf = new RandomAccessFile(filepath, "r")) {
byte[] magic = new byte[8];
raf.readFully(magic);
if (!java.util.Arrays.equals(magic, MAGIC)) {
throw new IOException("Not a valid .A file");
}
while (raf.getFilePointer() < raf.length()) {
byte[] header = new byte[HEADER_SIZE];
raf.readFully(header);
Member member = new Member();
member.name = new String(header, 0, 16, StandardCharsets.US_ASCII).trim().replaceAll("/$", "");
member.modificationTime = Long.parseLong(new String(header, 16, 12, StandardCharsets.US_ASCII).trim());
member.uid = Integer.parseInt(new String(header, 28, 6, StandardCharsets.US_ASCII).trim());
member.gid = Integer.parseInt(new String(header, 34, 6, StandardCharsets.US_ASCII).trim());
member.mode = Integer.parseInt(new String(header, 40, 8, StandardCharsets.US_ASCII).trim(), 8);
member.size = Long.parseLong(new String(header, 48, 10, StandardCharsets.US_ASCII).trim());
byte[] fmag = new byte[2];
System.arraycopy(header, 58, fmag, 0, 2);
if (!java.util.Arrays.equals(fmag, FMAG)) {
throw new IOException("Invalid header terminator");
}
member.data = new byte[(int) member.size];
raf.readFully(member.data);
if (member.size % 2 != 0) {
byte padding = raf.readByte();
if (padding != '\n') {
throw new IOException("Invalid padding");
}
}
members.add(member);
}
}
}
public void write(String outputPath) throws IOException {
if (outputPath == null) outputPath = filepath;
try (RandomAccessFile raf = new RandomAccessFile(outputPath, "rw")) {
raf.write(MAGIC);
for (Member member : members) {
String nameStr = String.format("%-16s", member.name);
String dateStr = String.format("%12d", member.modificationTime);
String uidStr = String.format("%6d", member.uid);
String gidStr = String.format("%6d", member.gid);
String modeStr = String.format("%8o", member.mode);
String sizeStr = String.format("%10d", member.size);
byte[] header = (nameStr + dateStr + uidStr + gidStr + modeStr + sizeStr + new String(FMAG, StandardCharsets.US_ASCII))
.getBytes(StandardCharsets.US_ASCII);
raf.write(header);
raf.write(member.data);
if (member.size % 2 != 0) {
raf.writeByte('\n');
}
}
}
}
public void addMember(String name, byte[] data, long modificationTime, int uid, int gid, int mode) {
Member member = new Member();
member.name = name.substring(0, Math.min(name.length(), 15));
member.modificationTime = modificationTime;
member.uid = uid;
member.gid = gid;
member.mode = mode;
member.size = data.length;
member.data = data;
members.add(member);
}
}
Usage example: AFileHandler handler = new AFileHandler("example.a"); handler.read(); handler.write("new.a");. Uses RandomAccessFile for reading/writing.
4. JavaScript Class
const fs = require('fs');
class AFileHandler {
static MAGIC = Buffer.from('!<arch>\n', 'ascii');
static HEADER_SIZE = 60;
static FMAG = Buffer.from('`\n', 'ascii');
constructor(filepath) {
this.filepath = filepath;
this.members = [];
}
read() {
const data = fs.readFileSync(this.filepath);
let offset = 0;
const magic = data.slice(offset, offset + 8);
if (!magic.equals(AFileHandler.MAGIC)) {
throw new Error('Not a valid .A file');
}
offset += 8;
while (offset < data.length) {
const header = data.slice(offset, offset + AFileHandler.HEADER_SIZE);
offset += AFileHandler.HEADER_SIZE;
const properties = {
name: header.slice(0, 16).toString('ascii').trim().replace(/\/$/, ''),
modification_time: parseInt(header.slice(16, 28).toString('ascii').trim(), 10),
uid: parseInt(header.slice(28, 34).toString('ascii').trim(), 10),
gid: parseInt(header.slice(34, 40).toString('ascii').trim(), 10),
mode: parseInt(header.slice(40, 48).toString('ascii').trim(), 8),
size: parseInt(header.slice(48, 58).toString('ascii').trim(), 10)
};
const fmag = header.slice(58, 60);
if (!fmag.equals(AFileHandler.FMAG)) {
throw new Error('Invalid header terminator');
}
const memberData = data.slice(offset, offset + properties.size);
offset += properties.size;
if (properties.size % 2 !== 0) {
const padding = data[offset];
if (padding !== 0x0a) { // \n
throw new Error('Invalid padding');
}
offset += 1;
}
this.members.push({ properties, data: memberData });
}
}
write(outputPath = this.filepath) {
let buffers = [AFileHandler.MAGIC];
for (const member of this.members) {
const props = member.properties;
const name = props.name.padEnd(16, ' ');
const date = props.modification_time.toString().padStart(12, ' ');
const uid = props.uid.toString().padStart(6, ' ');
const gid = props.gid.toString().padStart(6, ' ');
const mode = props.mode.toString(8).padStart(8, ' ');
const size = props.size.toString().padStart(10, ' ');
const headerStr = name + date + uid + gid + mode + size + '`\n';
buffers.push(Buffer.from(headerStr, 'ascii'));
buffers.push(member.data);
if (props.size % 2 !== 0) {
buffers.push(Buffer.from('\n', 'ascii'));
}
}
fs.writeFileSync(outputPath, Buffer.concat(buffers));
}
addMember(name, data, modification_time, uid = 0, gid = 0, mode = 0o644) {
const size = data.length;
const properties = {
name: name.slice(0, 15),
modification_time,
uid,
gid,
mode,
size
};
this.members.push({ properties, data: Buffer.from(data) });
}
}
Usage example: const handler = new AFileHandler('example.a'); handler.read(); handler.write('new.a');. Requires Node.js for fs.
5. C Class (Using C++ for Class Support)
Since standard C lacks classes, I'll use C++ (common for "C class" in such contexts). If pure C is needed, this can be adapted to structs and functions.
#include <fstream>
#include <string>
#include <vector>
#include <stdexcept>
#include <cstdio> // For sscanf, sprintf
#include <cstring> // For memcpy, memset
class AFileHandler {
private:
static const char MAGIC[9];
static const int HEADER_SIZE = 60;
static const char FMAG[3];
std::string filepath;
struct Member {
std::string name;
long modification_time;
int uid;
int gid;
int mode;
long size;
std::vector<char> data;
};
std::vector<Member> members;
public:
AFileHandler(const std::string& fp) : filepath(fp) {}
void read() {
std::ifstream file(filepath, std::ios::binary);
if (!file) throw std::runtime_error("Cannot open file");
char magic[8];
file.read(magic, 8);
if (std::strncmp(magic, MAGIC, 8) != 0) {
throw std::runtime_error("Not a valid .A file");
}
while (file) {
char header[HEADER_SIZE];
file.read(header, HEADER_SIZE);
if (file.gcount() < HEADER_SIZE) break;
Member member;
char name[17] = {0}, date[13] = {0}, uid[7] = {0}, gid[7] = {0}, mode[9] = {0}, size[11] = {0}, fmag[3] = {0};
std::memcpy(name, header, 16);
std::memcpy(date, header + 16, 12);
std::memcpy(uid, header + 28, 6);
std::memcpy(gid, header + 34, 6);
std::memcpy(mode, header + 40, 8);
std::memcpy(size, header + 48, 10);
std::memcpy(fmag, header + 58, 2);
if (std::strcmp(fmag, FMAG) != 0) {
throw std::runtime_error("Invalid header terminator");
}
member.name = std::string(name).substr(0, std::string(name).find_first_of(" /"));
sscanf(date, "%ld", &member.modification_time);
sscanf(uid, "%d", &member.uid);
sscanf(gid, "%d", &member.gid);
sscanf(mode, "%o", &member.mode);
sscanf(size, "%ld", &member.size);
member.data.resize(member.size);
file.read(member.data.data(), member.size);
if (member.size % 2 != 0) {
char padding;
file.read(&padding, 1);
if (padding != '\n') {
throw std::runtime_error("Invalid padding");
}
}
members.push_back(member);
}
}
void write(const std::string& output_path = "") {
std::string out = output_path.empty() ? filepath : output_path;
std::ofstream file(out, std::ios::binary);
if (!file) throw std::runtime_error("Cannot write file");
file.write(MAGIC, 8);
for (const auto& member : members) {
char header[HEADER_SIZE];
std::memset(header, ' ', HEADER_SIZE);
std::snprintf(header, 16 + 1, "%-16s", member.name.c_str());
std::snprintf(header + 16, 12 + 1, "%12ld", member.modification_time);
std::snprintf(header + 28, 6 + 1, "%6d", member.uid);
std::snprintf(header + 34, 6 + 1, "%6d", member.gid);
std::snprintf(header + 40, 8 + 1, "%8o", member.mode);
std::snprintf(header + 48, 10 + 1, "%10ld", member.size);
std::memcpy(header + 58, FMAG, 2);
file.write(header, HEADER_SIZE);
file.write(member.data.data(), member.size);
if (member.size % 2 != 0) {
file.write("\n", 1);
}
}
}
void add_member(const std::string& name, const std::vector<char>& data, long mod_time, int u = 0, int g = 0, int m = 0644) {
Member member;
member.name = name.substr(0, 15);
member.modification_time = mod_time;
member.uid = u;
member.gid = g;
member.mode = m;
member.size = data.size();
member.data = data;
members.push_back(member);
}
};
const char AFileHandler::MAGIC[9] = "!<arch>\n";
const char AFileHandler::FMAG[3] = "`\n";
Usage example: AFileHandler handler("example.a"); handler.read(); handler.write("new.a");. Compiles with C++11 or later.