sol: pset4/reverse

pset4/reverse/README.md

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+https://cs50.harvard.edu/x/2023/psets/4/reverse/

pset4/reverse/reverse.c

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+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "wav.h"
+
+int check_format(WAVHEADER header);
+int get_block_size(WAVHEADER header);
+
+int main(int argc, char *argv[])
+{
+    // Ensure proper usage
+    if (argc != 3)
+    {
+        printf("Usage: ./reverse input.wav output.wav\n");
+        return 1;
+    }
+
+    // Open input file for reading
+    FILE *input_wav = fopen(argv[1], "r");
+    if (input_wav == NULL)
+    {
+        printf("Could not open %s.\n", argv[1]);
+        return 1;
+    }
+
+    // Read header
+    WAVHEADER wav_header;
+    size_t read_bytes = fread(&wav_header, 1, sizeof(WAVHEADER), input_wav);
+    if (read_bytes != sizeof(WAVHEADER))
+    {
+        printf("Error reading header\n");
+        return 1;
+    }
+
+    // Use check_format to ensure WAV format
+    if (check_format(wav_header) != 0)
+    {
+        return 1;
+    }
+
+    // Open output file for writing
+    FILE *output_wav = fopen(argv[2], "w");
+    if (output_wav == NULL)
+    {
+        printf("Could not open file.\n");
+        return 1;
+    }
+
+    // Write header to output file
+    size_t written_bytes = fwrite(&wav_header, 1, read_bytes, output_wav);
+    if (written_bytes != read_bytes)
+    {
+        printf("Error writing to file\n");
+        return 1;
+    }
+
+    // Use get_block_size to calculate size of block
+    int block_size = get_block_size(wav_header);
+
+    // Move the pointer to start of the last block
+    fseek(input_wav, -block_size, SEEK_END);
+
+    // While input_wav pointer is not equal to the start of the audio data
+    // (or alternatively, is not equal to the end of WAVHEADER)
+    while (ftell(input_wav) >= (long) sizeof(WAVHEADER))
+    {
+        BYTE audio_buffer[block_size];
+        size_t read_block_bytes = fread(audio_buffer, 1, block_size, input_wav);
+        if (read_block_bytes != (size_t) block_size)
+        {
+            printf("Error reading block\n");
+            return 1;
+        }
+        size_t write_block_bytes = fwrite(audio_buffer, 1, read_block_bytes, output_wav);
+        if (read_block_bytes != write_block_bytes)
+        {
+            printf("Error writing block");
+            return 1;
+        }
+        // Iteratively move the input_wav pointer to the start of the previous block
+        // which is 2 blocks away since the pointer moved by 1 block earlier due to fread
+        fseek(input_wav, -2 * block_size, SEEK_CUR);
+    }
+
+    fclose(input_wav);
+    fclose(output_wav);
+}
+
+int check_format(WAVHEADER header)
+{
+    char *wave = "WAVE";
+    if (strncmp((const char *) header.format, wave, 4) == 0)
+    {
+        return 0;
+    }
+    return 1;
+}
+
+int get_block_size(WAVHEADER header)
+{
+    int bytes_per_sample = header.bitsPerSample / 8;
+    int num_channels = header.numChannels;
+    return num_channels * bytes_per_sample;
+}