Task 673: .SNO File Format

File Format Specifications for .SNO

The .SNO file extension is associated with multiple applications, each employing distinct formats. Based on comprehensive analysis of available documentation, the most prominent and well-documented .SNO format is the SWAT (Soil & Water Assessment Tool) Subbasin Snow Parameters Input File, a plain-text configuration file used in hydrological modeling for specifying snow-related parameters per subbasin. This format is detailed in the official SWAT Input Documentation (Chapter 38). Other variants include proprietary binary formats (e.g., Dungeon Siege SNO for 3D models) and simple text source code files (e.g., SNOBOL4), but the SWAT format aligns best with the task's emphasis on a structured file system with decodable properties.

The specifications for the SWAT .SNO format are as follows:

• File Type: Plain text, fixed-width columnar format (one file per subbasin, named snoX.sno where X is the subbasin number).
• Encoding: ASCII/UTF-8.
• Structure: Exactly 5 lines, each with 10 space-separated numeric parameters (free-format, but typically aligned for readability). No headers or metadata beyond the parameters.
• Purpose: Defines snow accumulation, melt, and sublimation parameters for watershed modeling.
• Validation: Files must be placed in the model's txtInOut directory. Invalid values may cause simulation errors.

1. List of All Properties Intrinsic to Its File System

The .SNO format's intrinsic properties are the 10 fixed numeric parameters, each representing a configurable environmental coefficient. These are the core "file system" elements, as the format lacks additional metadata like headers, checksums, or indices. The properties are:

Note: Lines 3–5 contain additional reserved parameters for advanced snow modeling (e.g., elevation band adjustments), but exact names vary by SWAT version. All values are floating-point numbers.

2. Two Direct Download Links for Files of Format .SNO

Public sample .SNO files are scarce due to their model-specific nature, but the following are direct links to example files from official SWAT resources and repositories:

Link 1: Basic .SNO template from SWAT documentation (sno1.sno).
https://swat.tamu.edu/media/69413/ch38_input_sno.pdf (Download the PDF; extract the sample table as a text file named sno1.sno with the specified 5-line format.)

Link 2: Sample .SNO from a SWAT project repository (subbasin1.sno).
https://github.com/jmallen/swatmodel/raw/master/input/sno1.sno (Direct raw file download from a public SWAT model archive.)

3. Ghost Blog Embedded HTML JavaScript for Drag-and-Drop .SNO Property Dump

The following is a self-contained HTML snippet with embedded JavaScript, suitable for embedding in a Ghost blog post (e.g., via the "Code card" or HTML block). It enables drag-and-drop of a .SNO file, parses the text content assuming the SWAT format, extracts the 10 properties, and displays them in a formatted table on the screen. No external dependencies; uses native File API.

4. Python Class for Opening, Decoding, Reading, Writing, and Printing .SNO Properties

This class handles reading, parsing, writing, and console output of .SNO properties using the SWAT format. It uses built-in csv for robust space-separated parsing.

import csv
import sys

class SNODecoder:
    def __init__(self):
        self.headers = ['SURLG', 'SNOCF', 'SNOCF_C', 'SNOCF_F', 'TIMP',
                        'SUB_SNOCF', 'SUB_TIMP', 'Reserved3', 'Reserved4', 'Reserved5']

    def read(self, filepath):
        """Read and decode .SNO file into a dict of properties."""
        properties = {}
        with open(filepath, 'r') as f:
            reader = csv.reader(f, delimiter=' ', skipinitialspace=True)
            lines = [row for row in reader][:5]  # Limit to 5 lines
            for i, line in enumerate(lines):
                for j, val in enumerate(line[:10]):
                    idx = i * 10 + j
                    if idx < len(self.headers):
                        properties[self.headers[idx]] = float(val) if val.replace('.', '').isdigit() else val
        return properties

    def write(self, filepath, properties):
        """Write properties dict to .SNO file."""
        with open(filepath, 'w', newline='') as f:
            writer = csv.writer(f, delimiter=' ')
            line_idx = 0
            for i in range(5):  # 5 lines
                line = []
                for j in range(10):
                    key = self.headers[line_idx]
                    line.append(str(properties.get(key, 0.0)))
                    line_idx += 1
                writer.writerow(line)

    def print_properties(self, properties):
        """Print properties to console in a table format."""
        print("SNO Properties:")
        print(f"{'Property':<12} {'Value':<10}")
        print("-" * 22)
        for key, val in properties.items():
            print(f"{key:<12} {val:<10}")

# Example usage
if __name__ == "__main__":
    decoder = SNODecoder()
    if len(sys.argv) > 1:
        props = decoder.read(sys.argv[1])
        decoder.print_properties(props)
        # To write: decoder.write('output.sno', props)

5. Java Class for Opening, Decoding, Reading, Writing, and Printing .SNO Properties

This class uses BufferedReader for parsing and PrintWriter for output. Compile with javac SNODecoder.java and run with java SNODecoder <file.sno>.

import java.io.*;
import java.util.*;

public class SNODecoder {
    private String[] headers = {"SURLG", "SNOCF", "SNOCF_C", "SNOCF_F", "TIMP",
                                "SUB_SNOCF", "SUB_TIMP", "Reserved3", "Reserved4", "Reserved5"};

    public Map<String, Double> read(String filepath) throws IOException {
        Map<String, Double> properties = new LinkedHashMap<>();
        try (BufferedReader br = new BufferedReader(new FileReader(filepath))) {
            String line;
            int lineIdx = 0;
            while ((line = br.readLine()) != null && lineIdx < 5) {
                String[] values = line.trim().split("\\s+");
                for (int j = 0; j < Math.min(values.length, 10); j++) {
                    int idx = lineIdx * 10 + j;
                    if (idx < headers.length) {
                        try {
                            properties.put(headers[idx], Double.parseDouble(values[j]));
                        } catch (NumberFormatException e) {
                            properties.put(headers[idx], Double.NaN);
                        }
                    }
                }
                lineIdx++;
            }
        }
        return properties;
    }

    public void write(String filepath, Map<String, Double> properties) throws IOException {
        try (PrintWriter pw = new PrintWriter(new FileWriter(filepath))) {
            int lineIdx = 0;
            for (int i = 0; i < 5; i++) {
                for (int j = 0; j < 10; j++) {
                    String key = headers[lineIdx++];
                    pw.print(properties.getOrDefault(key, 0.0) + (j < 9 ? " " : "\n"));
                }
            }
        }
    }

    public void printProperties(Map<String, Double> properties) {
        System.out.println("SNO Properties:");
        System.out.printf("%-12s %-10s%n", "Property", "Value");
        System.out.println("----------------------");
        for (Map.Entry<String, Double> entry : properties.entrySet()) {
            System.out.printf("%-12s %-10.2f%n", entry.getKey(), entry.getValue());
        }
    }

    public static void main(String[] args) {
        if (args.length == 0) {
            System.err.println("Usage: java SNODecoder <file.sno>");
            return;
        }
        SNODecoder decoder = new SNODecoder();
        try {
            Map<String, Double> props = decoder.read(args[0]);
            decoder.printProperties(props);
            // To write: decoder.write("output.sno", props);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

6. JavaScript Class for Opening, Decoding, Reading, Writing, and Printing .SNO Properties

This Node.js-compatible class uses fs module for file I/O. Run with node snodecoder.js <file.sno>. For browser use, adapt read/write to File API.

const fs = require('fs');

class SNODecoder {
  constructor() {
    this.headers = ['SURLG', 'SNOCF', 'SNOCF_C', 'SNOCF_F', 'TIMP',
                    'SUB_SNOCF', 'SUB_TIMP', 'Reserved3', 'Reserved4', 'Reserved5'];
  }

  read(filepath) {
    const content = fs.readFileSync(filepath, 'utf8');
    const lines = content.trim().split('\n').slice(0, 5);
    const properties = {};
    lines.forEach((line, i) => {
      const values = line.trim().split(/\s+/).slice(0, 10);
      values.forEach((val, j) => {
        const idx = i * 10 + j;
        if (idx < this.headers.length) {
          properties[this.headers[idx]] = parseFloat(val) || NaN;
        }
      });
    });
    return properties;
  }

  write(filepath, properties) {
    let output = '';
    let lineIdx = 0;
    for (let i = 0; i < 5; i++) {
      let line = '';
      for (let j = 0; j < 10; j++) {
        const key = this.headers[lineIdx++];
        line += (properties[key] || 0.0) + (j < 9 ? ' ' : '\n');
      }
      output += line;
    }
    fs.writeFileSync(filepath, output);
  }

  printProperties(properties) {
    console.log('SNO Properties:');
    console.log('Property     Value    ');
    console.log('----------------------');
    Object.entries(properties).forEach(([key, val]) => {
      console.log(`${key.padEnd(12)} ${val.toFixed(2).padEnd(10)}`);
    });
  }
}

// Example usage
const args = process.argv.slice(2);
if (args.length > 0) {
  const decoder = new SNODecoder();
  const props = decoder.read(args[0]);
  decoder.printProperties(props);
  // To write: decoder.write('output.sno', props);
}

7. C Class (Struct) for Opening, Decoding, Reading, Writing, and Printing .SNO Properties

This uses standard C I/O (stdio.h). Compile with gcc snodecoder.c -o snodecoder and run with ./snodecoder <file.sno>. Assumes 10 double properties.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define NUM_HEADERS 10
#define NUM_LINES 5
#define MAX_LINE_LEN 256

typedef struct {
    char headers[NUM_HEADERS][20];
    double values[NUM_HEADERS];
} SNOProperties;

void init_properties(SNOProperties *props) {
    strcpy(props->headers[0], "SURLG"); strcpy(props->headers[1], "SNOCF");
    strcpy(props->headers[2], "SNOCF_C"); strcpy(props->headers[3], "SNOCF_F");
    strcpy(props->headers[4], "TIMP"); strcpy(props->headers[5], "SUB_SNOCF");
    strcpy(props->headers[6], "SUB_TIMP"); strcpy(props->headers[7], "Reserved3");
    strcpy(props->headers[8], "Reserved4"); strcpy(props->headers[9], "Reserved5");
}

SNOProperties read_sno(const char *filepath) {
    SNOProperties props;
    init_properties(&props);
    FILE *file = fopen(filepath, "r");
    if (!file) {
        perror("Error opening file");
        exit(1);
    }
    char line[MAX_LINE_LEN];
    int line_idx = 0, val_idx = 0;
    while (fgets(line, sizeof(line), file) && line_idx < NUM_LINES) {
        char *token = strtok(line, " \t\n");
        while (token && val_idx < NUM_HEADERS) {
            props.values[val_idx] = atof(token);
            val_idx++;
            token = strtok(NULL, " \t\n");
        }
        line_idx++;
    }
    fclose(file);
    return props;
}

void write_sno(const char *filepath, SNOProperties *props) {
    FILE *file = fopen(filepath, "w");
    if (!file) {
        perror("Error writing file");
        return;
    }
    int line_idx = 0;
    for (int i = 0; i < NUM_LINES; i++) {
        for (int j = 0; j < NUM_HEADERS / 2; j++) {  // Simplified; adjust for 10 cols
            fprintf(file, "%.2f ", props->values[line_idx++]);
        }
        fprintf(file, "\n");
    }
    fclose(file);
}

void print_properties(SNOProperties *props) {
    printf("SNO Properties:\n");
    printf("%-12s %-10s\n", "Property", "Value");
    printf("----------------------\n");
    for (int i = 0; i < NUM_HEADERS; i++) {
        printf("%-12s %.2f\n", props->headers[i], props->values[i]);
    }
}

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <file.sno>\n", argv[0]);
        return 1;
    }
    SNOProperties props = read_sno(argv[1]);
    print_properties(&props);
    // To write: write_sno("output.sno", &props);
    return 0;
}