Add riffprobe

2 files changed, 182 insertions, 0 deletions

diff --git a/riffprobe/build.sh b/riffprobe/build.sh
new file mode 100755
index 0000000..51b6656
--- /dev/null
+++ b/riffprobe/build.sh
@@ -0,0 +1,4 @@
+#!/bin/sh
+set -euo pipefail
+mkdir -p bin
+cc -o bin/riffprobe -Wall -Wextra -Wpedantic -O0 -g ./riffprobe.c
diff --git a/riffprobe/riffprobe.c b/riffprobe/riffprobe.c
new file mode 100644
index 0000000..100b2fa
--- /dev/null
+++ b/riffprobe/riffprobe.c
@@ -0,0 +1,178 @@
+// ================================================================================================
+// 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;
+}