From 715b53059b73d762348b8c1f54d9aa5f65f5262f Mon Sep 17 00:00:00 2001
From: jakka <jakkadoujin@gmail.com>
Date: Wed, 25 Jun 2025 00:54:46 +0300
Subject: started working on my own libflac decoder

---
 src/flac/decoder.rs | 139 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 src/flac/decoder.rs

(limited to 'src/flac/decoder.rs')

diff --git a/src/flac/decoder.rs b/src/flac/decoder.rs
new file mode 100644
index 0000000..99ac36e
--- /dev/null
+++ b/src/flac/decoder.rs
@@ -0,0 +1,139 @@
+use std::{
+    error::Error,
+    ffi::{CString, c_void},
+    fmt::Display,
+    path::Path,
+};
+
+use libflac_sys::{
+    FLAC__STREAM_DECODER_INIT_STATUS_ALREADY_INITIALIZED,
+    FLAC__STREAM_DECODER_INIT_STATUS_ERROR_OPENING_FILE,
+    FLAC__STREAM_DECODER_INIT_STATUS_INVALID_CALLBACKS,
+    FLAC__STREAM_DECODER_INIT_STATUS_MEMORY_ALLOCATION_ERROR, FLAC__STREAM_DECODER_INIT_STATUS_OK,
+    FLAC__STREAM_DECODER_INIT_STATUS_UNSUPPORTED_CONTAINER, FLAC__StreamDecoder,
+    FLAC__StreamDecoderInitStatus, FLAC__bool, FLAC__stream_decoder_finish,
+    FLAC__stream_decoder_get_bits_per_sample, FLAC__stream_decoder_get_channels,
+    FLAC__stream_decoder_get_sample_rate, FLAC__stream_decoder_init_file, FLAC__stream_decoder_new,
+    FLAC__stream_decoder_process_single, FLAC__stream_decoder_set_md5_checking,
+};
+
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[repr(u32)]
+pub enum FlacDecoderInitError {
+    AlreadyInitialized = FLAC__STREAM_DECODER_INIT_STATUS_ALREADY_INITIALIZED,
+
+    ErrorOpeningFile = FLAC__STREAM_DECODER_INIT_STATUS_ERROR_OPENING_FILE,
+
+    InvalidCallbacks = FLAC__STREAM_DECODER_INIT_STATUS_INVALID_CALLBACKS,
+
+    MemoryAllocationError = FLAC__STREAM_DECODER_INIT_STATUS_MEMORY_ALLOCATION_ERROR,
+
+    UnsupportedContainer = FLAC__STREAM_DECODER_INIT_STATUS_UNSUPPORTED_CONTAINER,
+}
+
+impl Error for FlacDecoderInitError {}
+
+impl Display for FlacDecoderInitError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{self:?}")
+    }
+}
+
+impl From<FlacDecoderInitError> for FLAC__StreamDecoderInitStatus {
+    fn from(val: FlacDecoderInitError) -> Self {
+        val as FLAC__StreamDecoderInitStatus
+    }
+}
+
+impl TryFrom<FLAC__StreamDecoderInitStatus> for FlacDecoderInitError {
+    type Error = ();
+
+    #[allow(non_upper_case_globals)]
+    fn try_from(raw: FLAC__StreamDecoderInitStatus) -> Result<FlacDecoderInitError, ()> {
+        Ok(match raw {
+            FLAC__STREAM_DECODER_INIT_STATUS_ALREADY_INITIALIZED => {
+                FlacDecoderInitError::AlreadyInitialized
+            }
+            FLAC__STREAM_DECODER_INIT_STATUS_ERROR_OPENING_FILE => {
+                FlacDecoderInitError::ErrorOpeningFile
+            }
+            FLAC__STREAM_DECODER_INIT_STATUS_INVALID_CALLBACKS => {
+                FlacDecoderInitError::InvalidCallbacks
+            }
+            FLAC__STREAM_DECODER_INIT_STATUS_MEMORY_ALLOCATION_ERROR => {
+                FlacDecoderInitError::MemoryAllocationError
+            }
+            FLAC__STREAM_DECODER_INIT_STATUS_UNSUPPORTED_CONTAINER => {
+                FlacDecoderInitError::UnsupportedContainer
+            }
+            _ => return Err(()),
+        })
+    }
+}
+
+fn convert_path(path: &Path) -> CString {
+    CString::new(path.to_str().expect("non-UTF-8 filename")).expect("filename has internal NULs")
+}
+
+pub(crate) struct FlacDecoder(pub *mut FLAC__StreamDecoder);
+
+impl FlacDecoder {
+    pub(crate) fn new() -> Self {
+        FlacDecoder(unsafe { FLAC__stream_decoder_new() })
+    }
+
+    pub(crate) fn init_decode_from_file<P: AsRef<Path>>(
+        &self,
+        file: &P,
+        buf: &mut Vec<i32>,
+    ) -> Result<(), FlacDecoderInitError> {
+        unsafe {
+            FLAC__stream_decoder_set_md5_checking(self.0, true as FLAC__bool);
+        }
+
+        let filename = convert_path(file.as_ref());
+        unsafe {
+            let result: FLAC__StreamDecoderInitStatus = FLAC__stream_decoder_init_file(
+                self.0,
+                filename.as_ptr(),
+                None,
+                None,
+                None,
+                buf.as_mut_ptr() as *mut c_void,
+            );
+            if result != FLAC__STREAM_DECODER_INIT_STATUS_OK {
+                return Err(FlacDecoderInitError::try_from(result).unwrap());
+            }
+        }
+
+        Ok(())
+    }
+
+    pub(crate) fn decode_frame(&self) -> Result<(), ()> {
+        if unsafe { FLAC__stream_decoder_process_single(self.0) } != 0 {
+            Ok(())
+        } else {
+            Err(())
+        }
+    }
+
+    pub(crate) fn get_channels(&self) -> u32 {
+        unsafe { FLAC__stream_decoder_get_channels(self.0) }
+    }
+
+    pub(crate) fn get_bps(&self) -> u32 {
+        unsafe { FLAC__stream_decoder_get_bits_per_sample(self.0) }
+    }
+
+    pub(crate) fn get_samplerate(&self) -> u32 {
+        unsafe { FLAC__stream_decoder_get_sample_rate(self.0) }
+    }
+}
+
+impl Drop for FlacDecoder {
+    fn drop(&mut self) {
+        if !(self.0.is_null()) {
+            unsafe { FLAC__stream_decoder_finish(self.0) };
+        }
+    }
+}
-- 
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