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// ================================================================================================
// Basic RIFF/WAVE file traversal. Does not decode media data.
//
// ref: https://mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/Docs/riffmci.pdf
//
// Changelog:
// 9/20/2026: Initial release
//
// License:
// SPDX-License-Identifier: 0BSD
// Copyright (c) 2026 Hunter Kvalevog
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE.
// ================================================================================================
#include <ctype.h>
#include <errno.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef __GNUC__
# define ATTR_NORETURN __attribute__((noreturn))
# define ATTR_PRINTF(A1, A2) __attribute__((format(printf, A1, A2)))
#else
# define ATTR_NORETURN
# define ATTR_PRINTF(A1, A2)
#endif
ATTR_NORETURN
ATTR_PRINTF(1, 2)
static void die(const char *fmt, ...)
{
va_list va; va_start(va, fmt);
vprintf(fmt, va);
va_end(va);
exit(1);
}
typedef struct Chunk Chunk;
struct Chunk
{
uint32_t id;
uint32_t size;
};
// WAVE chunks
typedef struct WAVE_Fmt WAVE_Fmt;
struct WAVE_Fmt
{
uint16_t fmt_tag;
uint16_t channels;
uint32_t samples_per_sec;
uint32_t avg_bytes_per_sec;
uint16_t block_align;
};
static bool read_chunk(FILE *fp, Chunk *chunk)
{
return fread(chunk, sizeof(Chunk), 1, fp) == 1;
}
static const char *unfourcc(uint32_t id)
{
static char b[5] = { 0 };
b[0] = (id) & 0xFF;
b[1] = (id >> 8) & 0xFF;
b[2] = (id >> 16) & 0xFF;
b[3] = (id >> 24) & 0xFF;
return b;
}
static bool match_id(uint32_t id, const char *fourcc)
{
const char *id_fourcc = unfourcc(id);
for (int i = 0; i < 4; ++i)
{
if (tolower(id_fourcc[i]) != tolower(fourcc[i]))
return false;
}
return true;
}
static uint32_t pad_size(uint32_t size)
{
if (size % 2 != 0)
return size + 1;
return size;
}
int main(int argc, const char **argv)
{
if (argc < 2)
die("no file");
FILE* fp = fopen(argv[1], "rb");
if (!fp)
die("failed to open file: %s", strerror(errno));
fseek(fp, 0, SEEK_END);
size_t flen = ftell(fp);
fseek(fp, 0, SEEK_SET);
Chunk root;
if (!read_chunk(fp, &root) || !match_id(root.id, "RIFF"))
die("unsupported or malformed file");
if (root.size + sizeof(Chunk) != flen)
printf("file length mismatch\n");
uint32_t riff_type = 0;
fread(&riff_type, sizeof(riff_type), 1, fp);
printf("type: %s\n", unfourcc(riff_type));
Chunk chunk;
while (read_chunk(fp, &chunk))
{
size_t next_pos = ftell(fp) + pad_size(chunk.size);
printf("chunk: %s\n", unfourcc(chunk.id));
if (match_id(riff_type, "WAVE") && match_id(chunk.id, "FMT "))
{
WAVE_Fmt fmt;
fread(&fmt, sizeof(fmt), 1, fp);
printf(" fmt category: %d\n", fmt.fmt_tag);
printf(" channels: %d\n", fmt.channels);
printf(" sample rate: %d\n", fmt.samples_per_sec);
}
if (match_id(riff_type, "WAVE") && match_id(chunk.id, "FACT")) {
uint32_t file_size = 0;
fread(&file_size, sizeof(file_size), 1, fp);
printf(" file size: %d\n", file_size);
}
if (match_id(chunk.id, "LIST")) {
uint32_t list_type = 0;
fread(&list_type, sizeof(list_type), 1, fp);
printf(" list type: %s\n", unfourcc(list_type));
size_t list_start = ftell(fp);
size_t list_end = list_start + chunk.size - sizeof(list_type);
Chunk subchunk;
while ((size_t)ftell(fp) < list_end && read_chunk(fp, &subchunk))
{
size_t next_sub_pos = ftell(fp) + pad_size(subchunk.size);
printf(" subchunk: %s\n", unfourcc(subchunk.id));
if (match_id(subchunk.id, "IART") ||
match_id(subchunk.id, "IGNR") ||
match_id(subchunk.id, "IPRD") ||
match_id(subchunk.id, "ISFT"))
{
char buf[1024] = { 0 };
size_t len = sizeof(buf) - 1;
if (subchunk.size < len)
len = subchunk.size;
fread(buf, len, 1, fp);
printf(" data: %s\n", buf);
}
fseek(fp, next_sub_pos, SEEK_SET);
}
}
fseek(fp, next_pos, SEEK_SET);
}
fclose(fp);
return 0;
}
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