Add a standalone tool for decoding ffmpeg oss-fuzz samples

This tries to replicate the call sequence exercised by the
decoding fuzz tests for ffmpeg/oss-fuzz (matching what
tools/target_dec_fuzzer.c from ffmpeg does, when calling the
libfdk-aac decoder via libavcodec).

.gitignore

@@ -27,3 +27,4 @@ missing
 stamp-h1
 aac-enc
 compile
+fuzz-dec

Makefile.am

@@ -39,11 +39,14 @@ libfdk_aac_la_LDFLAGS = -version-info @FDK_AAC_VERSION@ -no-undefined \
     -export-symbols $(top_srcdir)/fdk-aac.sym
 
 if EXAMPLE
-bin_PROGRAMS = aac-enc$(EXEEXT)
+bin_PROGRAMS = aac-enc$(EXEEXT) fuzz-dec$(EXEEXT)
 
 aac_enc_LDADD = libfdk-aac.la
 aac_enc_SOURCES = aac-enc.c wavreader.c
 
+fuzz_dec_LDADD = libfdk-aac.la
+fuzz_dec_SOURCES = fuzz-dec.c
+
 noinst_HEADERS = wavreader.h
 endif
 

fuzz-dec.c

@@ -0,0 +1,94 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include "aacdecoder_lib.h"
+
+static const uint8_t tag[] = "FUZZ-TAG";
+
+static void test(const uint8_t *ptr, int size) {
+	const uint8_t *base = ptr;
+	const uint8_t *end = ptr + size;
+	int tagsize = sizeof(tag) - 1;
+
+	int decoder_buffer_size = 2048 * 2 * 8;
+	uint8_t *decoder_buffer = malloc(decoder_buffer_size);
+
+	HANDLE_AACDECODER decoder = aacDecoder_Open(TT_MP4_ADTS, 1);
+	aacDecoder_SetParam(decoder, AAC_CONCEAL_METHOD, 1);
+	aacDecoder_SetParam(decoder, AAC_PCM_LIMITER_ENABLE, 0);
+
+	while (1) {
+		const uint8_t* start = ptr;
+		UINT valid, buffer_size;
+		AAC_DECODER_ERROR err;
+
+		while (ptr + tagsize < end) {
+			if (!memcmp(ptr, tag, tagsize))
+				break;
+			ptr++;
+		}
+		if (ptr + tagsize > end)
+			ptr = end;
+
+		do {
+			valid = buffer_size = ptr - start;
+			err = aacDecoder_Fill(decoder, (UCHAR**) &start, &buffer_size, &valid);
+			start += buffer_size - valid;
+			if (err == AAC_DEC_NOT_ENOUGH_BITS)
+				continue;
+			if (err == AAC_DEC_OK)
+				err = aacDecoder_DecodeFrame(decoder, (INT_PCM *) decoder_buffer, decoder_buffer_size / sizeof(INT_PCM), 0);
+			if (err != AAC_DEC_NOT_ENOUGH_BITS && err != AAC_DEC_OK)
+				break;
+		} while (start < ptr);
+
+		aacDecoder_GetStreamInfo(decoder);
+
+		if (ptr + tagsize <= end) {
+			ptr += tagsize;
+		} else {
+			break;
+		}
+	}
+	while (1) {
+		const uint8_t* start = NULL;
+		UINT buffer_size = 0, valid = 0;
+		AAC_DECODER_ERROR err;
+		err = aacDecoder_Fill(decoder, (UCHAR**) &start, &buffer_size, &valid);
+		if (err == AAC_DEC_OK)
+			err = aacDecoder_DecodeFrame(decoder, (INT_PCM *) decoder_buffer, decoder_buffer_size / sizeof(INT_PCM), 0);
+		if (err != AAC_DEC_OK)
+			break;
+	}
+	free(decoder_buffer);
+	aacDecoder_Close(decoder);
+}
+
+int main(int argc, char *argv[]) {
+	FILE *f;
+	int size;
+	uint8_t *buf;
+
+	if (argc < 2) {
+		printf("%s file\n", argv[0]);
+		return 0;
+	}
+	f = fopen(argv[1], "rb");
+	if (!f) {
+		perror(argv[1]);
+		return 1;
+	}
+
+	fseek(f, 0, SEEK_END);
+	size = ftell(f);
+	fseek(f, 0, SEEK_SET);
+
+	buf = malloc(size);
+	if (fread(buf, 1, size, f) == size)
+		test(buf, size);
+	free(buf);
+
+	fclose(f);
+	return 0;
+}