fix: get rid of a use-after-free bug that happens when using the default heap allocator

TODO.md

@@ -4,11 +4,7 @@ Files:-
 	  if they are, then the blocking strategy is VARIABLE, if not, then it's FIXED.
 
 Playback issues in the example program that may relate to the decoder:-
-05 - CRC fails for a frame. The gotten CRC is different each time, expected CRC is also different sometimes.
-06 - Same as above
 23 - Crunchy loud noise mixed with the actual audio data
-25 - Same CRC problem
-It's worth noting that if we get rid of the CRC checks the files play just fine.
 
 uncommon/04 -> We get a bits per sample mismatch
 uncommon/10 -> We error with Invalid Signature. I assume for these two I should look for the frame sync bits. But maybe my decoder should reject these. idk.

buffer.odin

@@ -0,0 +1,48 @@
+package flac
+
+import "core:io"
+
+// Buffer is a very minimal writable buffer based on bytes.Buffer
+Buffer :: struct {
+	buf: [dynamic]byte,
+}
+
+buffer_init_allocator :: proc(b: ^Buffer, len, cap: int, allocator := context.allocator, loc := #caller_location) {
+	b.buf = make([dynamic]byte, len, cap, allocator, loc)
+}
+
+buffer_write :: proc(b: ^Buffer, p: []byte) -> (n: int, err: io.Error) {
+	return append(&b.buf, ..p), nil
+}
+
+buffer_destroy :: proc(b: ^Buffer) {
+	delete(b.buf)
+}
+
+buffer_to_bytes :: proc(b: ^Buffer) -> []byte {
+	return b.buf[:]
+}
+
+buffer_to_stream :: proc(b: ^Buffer) -> (s: io.Stream) {
+	s.data = b
+	s.procedure = _buffer_proc
+	return
+}
+
+@(private)
+_buffer_proc :: proc(stream_data: rawptr, mode: io.Stream_Mode, p: []byte, offset: i64, whence: io.Seek_From) -> (n: i64, err: io.Error) {
+	b := (^Buffer)(stream_data)
+	#partial switch mode {
+	case .Write:
+		return io._i64_err(buffer_write(b, p))
+	case .Size:
+		n = i64(cap(b.buf))
+		return
+	case .Destroy:
+		buffer_destroy(b)
+		return
+	case .Query:
+		return io.query_utility({.Write, .Size, .Destroy})
+	}
+	return 0, .Empty
+}

examples/buffered/main.odin

@@ -17,6 +17,7 @@ main :: proc() {
         fmt.eprintln("Please provide a path to a flac file.")
         os.exit(1)
     }
+    defer delete(os.args)
 
     arena: virtual.Arena
     handle: ^alsa.pcm_t
@@ -53,12 +54,10 @@ main :: proc() {
     sample_rate := flac_data.metadata.sample_rate
     channels := flac_data.metadata.channels
 
-    //md5_ctx: md5.Context
-    //md5.init(&md5_ctx)
+    md5_ctx: md5.Context
+    md5.init(&md5_ctx)
     for {
-        frame, err := flac.read_next_frame(reader, flac_data)
-
-        defer delete(frame.samples)
+        frame, err := flac.read_next_frame(reader, flac_data, allocator)
         if err != nil {
             if err == .EOF {
                 break
@@ -99,15 +98,15 @@ main :: proc() {
         }
         fmt.printfln("Played %d frames", frames)
 
-        //flac.md5hash(&md5_ctx, flac_data.metadata.bits_per_sample, samples)
+        flac.md5hash(&md5_ctx, flac_data.metadata.bits_per_sample, frame.samples)
     }
     end := time.now()
 
-    //err = flac.md5sum(&md5_ctx, flac_data)
-    //if err == .MD5_Mismatch {
-    //    fmt.println("Decoded audio data is not correct.")
-    //    os.exit(1)
-    //}
+    err = flac.md5sum(&md5_ctx, flac_data)
+    if err == .MD5_Mismatch {
+        fmt.println("Decoded audio data is not correct.")
+        os.exit(1)
+    }
 
     alsa_err = alsa.pcm_drain(handle)
     if alsa_err < 0 {

examples/in_memory/main.odin

@@ -16,6 +16,7 @@ main :: proc() {
         fmt.eprintln("Please provide a path to a flac file.")
         os.exit(1)
     }
+	defer delete(os.args)
 
     handle: ^alsa.pcm_t
 
@@ -61,14 +62,12 @@ main :: proc() {
         converted_samples[i] = i16(new_sample)
     }
 
-    for {
     frames := alsa.pcm_writei(handle, raw_data(converted_samples), u64(len(flac_data.samples)) / u64(flac_data.metadata.channels))
     if frames < 0 {
         fmt.eprintln("Error writing to PCM device:", alsa.strerror(auto_cast frames))
-            break
+		return
     }
     fmt.printfln("Played %d frames", frames)
-    }
 
     alsa_err = alsa.pcm_drain(handle)
     if alsa_err < 0 {

flac.odin

@@ -852,15 +852,17 @@ read_metadata :: proc(r: ^Reader, buffered := false, allocator := context.alloca
     return flac, nil
 }
 
-read_next_frame :: proc(r: ^Reader, flac: ^Flac) -> (frame: Frame, err: Error) {
+read_next_frame :: proc(r: ^Reader, flac: ^Flac, allocator := context.allocator) -> (frame: Frame, err: Error) {
     //
     // Frame Header
     //
+    context.allocator = allocator
     tee_r: io.Tee_Reader
-    crc_buffer: bytes.Buffer
-    bytes.buffer_init_allocator(&crc_buffer, 0, 128)
-    defer bytes.buffer_destroy(&crc_buffer)
-    crc := bytes.buffer_to_stream(&crc_buffer)
+
+    crc_buffer: Buffer
+    buffer_init_allocator(&crc_buffer, 0, 128, context.temp_allocator)
+
+    crc := buffer_to_stream(&crc_buffer)
     r := &Reader{
         r = io.tee_reader_init(&tee_r, r, crc),
         buf = r.buf,
@@ -960,7 +962,7 @@ read_next_frame :: proc(r: ^Reader, flac: ^Flac) -> (frame: Frame, err: Error) {
     // TODO: sample rate MUST NOT be 0 if the subframe contains audio.
     // a sample rate of 0 MAY be used when non-audio is represented.
 
-    crc8_bytes := bytes.buffer_to_bytes(&crc_buffer)
+    crc8_bytes := buffer_to_bytes(&crc_buffer)
     frame_header_crc := u8(read_bits(r, 8) or_return)
     calculated_header_crc := calculate_crc8(crc8_bytes)
 
@@ -1064,7 +1066,7 @@ read_next_frame :: proc(r: ^Reader, flac: ^Flac) -> (frame: Frame, err: Error) {
     //
     // Frame Footer
     //
-    crc16_bytes := bytes.buffer_to_bytes(&crc_buffer)
+    crc16_bytes := buffer_to_bytes(&crc_buffer)
     frame_crc := u16(read_data(r, u16be) or_return)
     calculated_frame_crc := calculate_crc16(crc16_bytes)
 
@@ -1101,7 +1103,7 @@ md5hash :: proc(md5_ctx: ^md5.Context, bps: u8, samples: []i32) {
 }
 
 md5sum :: proc(md5_ctx: ^md5.Context, flac: ^Flac) -> Error {
-    calculated_md5: [16]byte
+    calculated_md5 := [16]byte{}
     md5.final(md5_ctx, calculated_md5[:])
 
     flac.metadata.calculated_md5 = calculated_md5