[FL-2655, FL-2650] Buffered file streams (#1424)

* Initial buffered file stream implementation
* Fix logical errors
* Fix more logical errors
* Minimally working implementation
* Adapt infrared unit tests for buffered streams
* Increase read buffer size from 512 to 1K
* Correct naming and formatting
* More code improvements
* Allow passing access and open modes for buffered streams
* Implement tests for buffered streams
* Better file and method names
* Add comments and correct formatting
* Use buffered streams in Infrared
* Fix compilation error

applications/infrared/infrared_brute_force.c

@@ -51,9 +51,9 @@ bool infrared_brute_force_calculate_messages(InfraredBruteForce* brute_force) {
     bool success = false;
 
     Storage* storage = furi_record_open("storage");
-    FlipperFormat* ff = flipper_format_file_alloc(storage);
+    FlipperFormat* ff = flipper_format_buffered_file_alloc(storage);
 
-    success = flipper_format_file_open_existing(ff, brute_force->db_filename);
+    success = flipper_format_buffered_file_open_existing(ff, brute_force->db_filename);
     if(success) {
         string_t signal_name;
         string_init(signal_name);
@@ -95,8 +95,9 @@ bool infrared_brute_force_start(
 
     if(*record_count) {
         Storage* storage = furi_record_open("storage");
-        brute_force->ff = flipper_format_file_alloc(storage);
+        brute_force->ff = flipper_format_buffered_file_alloc(storage);
-        success = flipper_format_file_open_existing(brute_force->ff, brute_force->db_filename);
+        success =
+            flipper_format_buffered_file_open_existing(brute_force->ff, brute_force->db_filename);
         if(!success) {
             flipper_format_free(brute_force->ff);
             brute_force->ff = NULL;

applications/infrared/infrared_remote.c

@@ -140,13 +140,13 @@ bool infrared_remote_store(InfraredRemote* remote) {
 
 bool infrared_remote_load(InfraredRemote* remote, string_t path) {
     Storage* storage = furi_record_open("storage");
-    FlipperFormat* ff = flipper_format_file_alloc(storage);
+    FlipperFormat* ff = flipper_format_buffered_file_alloc(storage);
 
     string_t buf;
     string_init(buf);
 
     FURI_LOG_I(TAG, "load file: \'%s\'", string_get_cstr(path));
-    bool success = flipper_format_file_open_existing(ff, string_get_cstr(path));
+    bool success = flipper_format_buffered_file_open_existing(ff, string_get_cstr(path));
 
     if(success) {
         uint32_t version;

applications/unit_tests/infrared/infrared_test.c

@@ -22,7 +22,7 @@ static void infrared_test_alloc() {
     test = malloc(sizeof(InfraredTest));
     test->decoder_handler = infrared_alloc_decoder();
     test->encoder_handler = infrared_alloc_encoder();
-    test->ff = flipper_format_file_alloc(storage);
+    test->ff = flipper_format_buffered_file_alloc(storage);
     string_init(test->file_path);
 }
 
@@ -52,7 +52,8 @@ static bool infrared_test_prepare_file(const char* protocol_name) {
 
     do {
         uint32_t format_version;
-        if(!flipper_format_file_open_existing(test->ff, string_get_cstr(test->file_path))) break;
+        if(!flipper_format_buffered_file_open_existing(test->ff, string_get_cstr(test->file_path)))
+            break;
         if(!flipper_format_read_header(test->ff, file_type, &format_version)) break;
         if(string_cmp_str(file_type, "IR tests file") || format_version != 1) break;
         success = true;
@@ -230,7 +231,7 @@ static void infrared_test_run_encoder(InfraredProtocol protocol, uint32_t test_i
             test->ff, string_get_cstr(buf), &expected_timings, &expected_timings_count),
         "Failed to load raw signal from file");
 
-    flipper_format_file_close(test->ff);
+    flipper_format_buffered_file_close(test->ff);
     string_clear(buf);
 
     uint32_t j = 0;
@@ -280,7 +281,7 @@ static void infrared_test_run_encoder_decoder(InfraredProtocol protocol, uint32_
             test->ff, string_get_cstr(buf), &input_messages, &input_messages_count),
         "Failed to load messages from file");
 
-    flipper_format_file_close(test->ff);
+    flipper_format_buffered_file_close(test->ff);
     string_clear(buf);
 
     for(uint32_t message_counter = 0; message_counter < input_messages_count; ++message_counter) {
@@ -343,7 +344,7 @@ static void infrared_test_run_decoder(InfraredProtocol protocol, uint32_t test_i
         infrared_test_load_messages(test->ff, string_get_cstr(buf), &messages, &messages_count),
         "Failed to load messages from file");
 
-    flipper_format_file_close(test->ff);
+    flipper_format_buffered_file_close(test->ff);
     string_clear(buf);
 
     InfraredMessage message_decoded_check_local;

applications/unit_tests/stream/stream_test.c

@@ -2,6 +2,7 @@
 #include <toolbox/stream/stream.h>
 #include <toolbox/stream/string_stream.h>
 #include <toolbox/stream/file_stream.h>
+#include <toolbox/stream/buffered_file_stream.h>
 #include <storage/storage.h>
 #include "../minunit.h"
 
@@ -282,6 +283,13 @@ MU_TEST(stream_composite_test) {
     mu_check(file_stream_open(stream, "/ext/filestream.str", FSAM_READ_WRITE, FSOM_CREATE_ALWAYS));
     MU_RUN_TEST_1(stream_composite_subtest, stream);
     stream_free(stream);
+
+    // test buffered file stream
+    stream = buffered_file_stream_alloc(storage);
+    mu_check(buffered_file_stream_open(
+        stream, "/ext/filestream.str", FSAM_READ_WRITE, FSOM_CREATE_ALWAYS));
+    MU_RUN_TEST_1(stream_composite_subtest, stream);
+    stream_free(stream);
     furi_record_close("storage");
 }
 
@@ -366,13 +374,101 @@ MU_TEST(stream_split_test) {
     mu_check(file_stream_open(stream, "/ext/filestream.str", FSAM_READ_WRITE, FSOM_CREATE_ALWAYS));
     MU_RUN_TEST_1(stream_split_subtest, stream);
     stream_free(stream);
+
+    // test buffered stream
+    stream = buffered_file_stream_alloc(storage);
+    mu_check(buffered_file_stream_open(
+        stream, "/ext/filestream.str", FSAM_READ_WRITE, FSOM_CREATE_ALWAYS));
+    MU_RUN_TEST_1(stream_split_subtest, stream);
+    stream_free(stream);
+
     furi_record_close("storage");
 }
 
+MU_TEST(stream_buffered_large_file_test) {
+    string_t input_data;
+    string_t output_data;
+    string_init(input_data);
+    string_init(output_data);
+
+    Storage* storage = furi_record_open("storage");
+
+    // generate test data consisting of several identical lines
+    const size_t data_size = 4096;
+    const size_t line_size = strlen(stream_test_data);
+    const size_t rep_count = data_size / line_size + 1;
+
+    for(size_t i = 0; i < rep_count; ++i) {
+        string_cat_printf(input_data, "%s\n", stream_test_data);
+    }
+
+    // write test data to file
+    Stream* stream = buffered_file_stream_alloc(storage);
+    mu_check(buffered_file_stream_open(
+        stream, "/ext/filestream.str", FSAM_READ_WRITE, FSOM_CREATE_ALWAYS));
+    mu_assert_int_eq(0, stream_size(stream));
+    mu_assert_int_eq(string_size(input_data), stream_write_string(stream, input_data));
+    mu_assert_int_eq(string_size(input_data), stream_size(stream));
+
+    const size_t substr_start = 8;
+    const size_t substr_len = 11;
+
+    mu_check(stream_seek(stream, substr_start, StreamOffsetFromStart));
+    mu_assert_int_eq(substr_start, stream_tell(stream));
+
+    // copy one substring from test data
+    char test_substr[substr_len + 1];
+    memset(test_substr, 0, substr_len + 1);
+    memcpy(test_substr, stream_test_data + substr_start, substr_len);
+
+    char buf[substr_len + 1];
+    memset(buf, 0, substr_len + 1);
+
+    // read substring
+    mu_assert_int_eq(substr_len, stream_read(stream, (uint8_t*)buf, substr_len));
+    mu_assert_string_eq(test_substr, buf);
+    memset(buf, 0, substr_len + 1);
+
+    // forward seek to cause a cache miss
+    mu_check(stream_seek(
+        stream, (line_size + 1) * (rep_count - 1) - substr_len, StreamOffsetFromCurrent));
+    // read same substring from a different line
+    mu_assert_int_eq(substr_len, stream_read(stream, (uint8_t*)buf, substr_len));
+    mu_assert_string_eq(test_substr, buf);
+    memset(buf, 0, substr_len + 1);
+
+    // backward seek to cause a cache miss
+    mu_check(stream_seek(
+        stream, -((line_size + 1) * (rep_count - 1) + substr_len), StreamOffsetFromCurrent));
+    mu_assert_int_eq(substr_len, stream_read(stream, (uint8_t*)buf, substr_len));
+    mu_assert_string_eq(test_substr, buf);
+
+    // read the whole file
+    mu_check(stream_rewind(stream));
+    string_t tmp;
+    string_init(tmp);
+    while(stream_read_line(stream, tmp)) {
+        string_cat(output_data, tmp);
+    }
+    string_clear(tmp);
+
+    // check against generated data
+    mu_assert_int_eq(string_size(input_data), string_size(output_data));
+    mu_check(string_equal_p(input_data, output_data));
+    mu_check(stream_eof(stream));
+
+    stream_free(stream);
+
+    furi_record_close("storage");
+    string_clear(input_data);
+    string_clear(output_data);
+}
+
 MU_TEST_SUITE(stream_suite) {
     MU_RUN_TEST(stream_write_read_save_load_test);
     MU_RUN_TEST(stream_composite_test);
     MU_RUN_TEST(stream_split_test);
+    MU_RUN_TEST(stream_buffered_large_file_test);
 }
 
 int run_minunit_test_stream() {

lib/flipper_format/flipper_format.c

@@ -2,6 +2,7 @@
 #include <toolbox/stream/stream.h>
 #include <toolbox/stream/string_stream.h>
 #include <toolbox/stream/file_stream.h>
+#include <toolbox/stream/buffered_file_stream.h>
 #include "flipper_format.h"
 #include "flipper_format_i.h"
 #include "flipper_format_stream.h"
@@ -36,11 +37,24 @@ FlipperFormat* flipper_format_file_alloc(Storage* storage) {
     return flipper_format;
 }
 
+FlipperFormat* flipper_format_buffered_file_alloc(Storage* storage) {
+    FlipperFormat* flipper_format = malloc(sizeof(FlipperFormat));
+    flipper_format->stream = buffered_file_stream_alloc(storage);
+    flipper_format->strict_mode = false;
+    return flipper_format;
+}
+
 bool flipper_format_file_open_existing(FlipperFormat* flipper_format, const char* path) {
     furi_assert(flipper_format);
     return file_stream_open(flipper_format->stream, path, FSAM_READ_WRITE, FSOM_OPEN_EXISTING);
 }
 
+bool flipper_format_buffered_file_open_existing(FlipperFormat* flipper_format, const char* path) {
+    furi_assert(flipper_format);
+    return buffered_file_stream_open(
+        flipper_format->stream, path, FSAM_READ_WRITE, FSOM_OPEN_EXISTING);
+}
+
 bool flipper_format_file_open_append(FlipperFormat* flipper_format, const char* path) {
     furi_assert(flipper_format);
 
@@ -87,6 +101,11 @@ bool flipper_format_file_close(FlipperFormat* flipper_format) {
     return file_stream_close(flipper_format->stream);
 }
 
+bool flipper_format_buffered_file_close(FlipperFormat* flipper_format) {
+    furi_assert(flipper_format);
+    return buffered_file_stream_close(flipper_format->stream);
+}
+
 void flipper_format_free(FlipperFormat* flipper_format) {
     furi_assert(flipper_format);
     stream_free(flipper_format->stream);

lib/flipper_format/flipper_format.h

@@ -115,6 +115,12 @@ FlipperFormat* flipper_format_string_alloc();
  */
 FlipperFormat* flipper_format_file_alloc(Storage* storage);
 
+/**
+ * Allocate FlipperFormat as file, buffered read-only mode.
+ * @return FlipperFormat* pointer to a FlipperFormat instance
+ */
+FlipperFormat* flipper_format_buffered_file_alloc(Storage* storage);
+
 /**
  * Open existing file. 
  * Use only if FlipperFormat allocated as a file.
@@ -124,6 +130,15 @@ FlipperFormat* flipper_format_file_alloc(Storage* storage);
  */
 bool flipper_format_file_open_existing(FlipperFormat* flipper_format, const char* path);
 
+/**
+ * Open existing file, read-only with buffered read operations.
+ * Use only if FlipperFormat allocated as a file.
+ * @param flipper_format Pointer to a FlipperFormat instance
+ * @param path File path
+ * @return True on success
+ */
+bool flipper_format_buffered_file_open_existing(FlipperFormat* flipper_format, const char* path);
+
 /**
  * Open existing file for writing and add values to the end of file. 
  * Use only if FlipperFormat allocated as a file.
@@ -159,6 +174,14 @@ bool flipper_format_file_open_new(FlipperFormat* flipper_format, const char* pat
  */
 bool flipper_format_file_close(FlipperFormat* flipper_format);
 
+/**
+ * Closes the file, use only if FlipperFormat allocated as a buffered file.
+ * @param flipper_format
+ * @return true
+ * @return false
+ */
+bool flipper_format_buffered_file_close(FlipperFormat* flipper_format);
+
 /**
  * Free FlipperFormat.
  * @param flipper_format Pointer to a FlipperFormat instance

lib/toolbox/stream/buffered_file_stream.c

@@ -0,0 +1,155 @@
+#include "buffered_file_stream.h"
+
+#include "stream_i.h"
+#include "file_stream.h"
+#include "stream_cache.h"
+
+typedef struct {
+    Stream stream_base;
+    Stream* file_stream;
+    StreamCache* cache;
+} BufferedFileStream;
+
+static void buffered_file_stream_free(BufferedFileStream* stream);
+static bool buffered_file_stream_eof(BufferedFileStream* stream);
+static void buffered_file_stream_clean(BufferedFileStream* stream);
+static bool
+    buffered_file_stream_seek(BufferedFileStream* stream, int32_t offset, StreamOffset offset_type);
+static size_t buffered_file_stream_tell(BufferedFileStream* stream);
+static size_t buffered_file_stream_size(BufferedFileStream* stream);
+static size_t
+    buffered_file_stream_write(BufferedFileStream* stream, const uint8_t* data, size_t size);
+static size_t buffered_file_stream_read(BufferedFileStream* stream, uint8_t* data, size_t size);
+static bool buffered_file_stream_delete_and_insert(
+    BufferedFileStream* stream,
+    size_t delete_size,
+    StreamWriteCB write_callback,
+    const void* ctx);
+
+const StreamVTable buffered_file_stream_vtable = {
+    .free = (StreamFreeFn)buffered_file_stream_free,
+    .eof = (StreamEOFFn)buffered_file_stream_eof,
+    .clean = (StreamCleanFn)buffered_file_stream_clean,
+    .seek = (StreamSeekFn)buffered_file_stream_seek,
+    .tell = (StreamTellFn)buffered_file_stream_tell,
+    .size = (StreamSizeFn)buffered_file_stream_size,
+    .write = (StreamWriteFn)buffered_file_stream_write,
+    .read = (StreamReadFn)buffered_file_stream_read,
+    .delete_and_insert = (StreamDeleteAndInsertFn)buffered_file_stream_delete_and_insert,
+};
+
+Stream* buffered_file_stream_alloc(Storage* storage) {
+    BufferedFileStream* stream = malloc(sizeof(BufferedFileStream));
+
+    stream->file_stream = file_stream_alloc(storage);
+    stream->cache = stream_cache_alloc();
+
+    stream->stream_base.vtable = &buffered_file_stream_vtable;
+    return (Stream*)stream;
+}
+
+bool buffered_file_stream_open(
+    Stream* _stream,
+    const char* path,
+    FS_AccessMode access_mode,
+    FS_OpenMode open_mode) {
+    furi_assert(_stream);
+    BufferedFileStream* stream = (BufferedFileStream*)_stream;
+    stream_cache_drop(stream->cache);
+    furi_check(stream->stream_base.vtable == &buffered_file_stream_vtable);
+    return file_stream_open(stream->file_stream, path, access_mode, open_mode);
+}
+
+bool buffered_file_stream_close(Stream* _stream) {
+    furi_assert(_stream);
+    BufferedFileStream* stream = (BufferedFileStream*)_stream;
+    furi_check(stream->stream_base.vtable == &buffered_file_stream_vtable);
+    return file_stream_close(stream->file_stream);
+}
+
+FS_Error buffered_file_stream_get_error(Stream* _stream) {
+    furi_assert(_stream);
+    BufferedFileStream* stream = (BufferedFileStream*)_stream;
+    furi_check(stream->stream_base.vtable == &buffered_file_stream_vtable);
+    return file_stream_get_error(stream->file_stream);
+}
+
+static void buffered_file_stream_free(BufferedFileStream* stream) {
+    furi_assert(stream);
+    stream_free(stream->file_stream);
+    stream_cache_free(stream->cache);
+    free(stream);
+}
+
+static bool buffered_file_stream_eof(BufferedFileStream* stream) {
+    return stream_cache_at_end(stream->cache) && stream_eof(stream->file_stream);
+}
+
+static void buffered_file_stream_clean(BufferedFileStream* stream) {
+    stream_cache_drop(stream->cache);
+    stream_clean(stream->file_stream);
+}
+
+static bool buffered_file_stream_seek(
+    BufferedFileStream* stream,
+    int32_t offset,
+    StreamOffset offset_type) {
+    bool success = false;
+    int32_t new_offset = offset;
+
+    if(offset_type == StreamOffsetFromCurrent) {
+        new_offset -= stream_cache_seek(stream->cache, offset);
+        if(new_offset < 0) {
+            new_offset -= (int32_t)stream_cache_size(stream->cache);
+        }
+    }
+
+    if((new_offset != 0) || (offset_type != StreamOffsetFromCurrent)) {
+        stream_cache_drop(stream->cache);
+        success = stream_seek(stream->file_stream, new_offset, offset_type);
+    } else {
+        success = true;
+    }
+
+    return success;
+}
+
+static size_t buffered_file_stream_tell(BufferedFileStream* stream) {
+    return stream_tell(stream->file_stream) + stream_cache_pos(stream->cache) -
+           stream_cache_size(stream->cache);
+}
+
+static size_t buffered_file_stream_size(BufferedFileStream* stream) {
+    return stream_cache_size(stream->cache) + stream_size(stream->file_stream);
+}
+
+static size_t
+    buffered_file_stream_write(BufferedFileStream* stream, const uint8_t* data, size_t size) {
+    stream_cache_drop(stream->cache);
+    return stream_write(stream->file_stream, data, size);
+}
+
+static size_t buffered_file_stream_read(BufferedFileStream* stream, uint8_t* data, size_t size) {
+    size_t need_to_read = size;
+
+    while(need_to_read) {
+        need_to_read -=
+            stream_cache_read(stream->cache, data + (size - need_to_read), need_to_read);
+        if(need_to_read) {
+            if(!stream_cache_fill(stream->cache, stream->file_stream)) {
+                break;
+            }
+        }
+    }
+
+    return size - need_to_read;
+}
+
+static bool buffered_file_stream_delete_and_insert(
+    BufferedFileStream* stream,
+    size_t delete_size,
+    StreamWriteCB write_callback,
+    const void* ctx) {
+    stream_cache_drop(stream->cache);
+    return stream_delete_and_insert(stream->file_stream, delete_size, write_callback, ctx);
+}

lib/toolbox/stream/buffered_file_stream.h

@@ -0,0 +1,47 @@
+#pragma once
+#include <stdlib.h>
+#include <storage/storage.h>
+#include "stream.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Allocate a file stream with buffered read operations
+ * @return Stream*
+ */
+Stream* buffered_file_stream_alloc(Storage* storage);
+
+/**
+ * Opens an existing file or creates a new one.
+ * @param stream pointer to file stream object.
+ * @param path path to file
+ * @param access_mode access mode from FS_AccessMode
+ * @param open_mode open mode from FS_OpenMode
+ * @return success flag. You need to close the file even if the open operation failed.
+ */
+bool buffered_file_stream_open(
+    Stream* stream,
+    const char* path,
+    FS_AccessMode access_mode,
+    FS_OpenMode open_mode);
+
+/**
+ * Closes the file.
+ * @param stream
+ * @return true
+ * @return false
+ */
+bool buffered_file_stream_close(Stream* stream);
+
+/**
+ * Retrieves the error id from the file object
+ * @param stream pointer to stream object.
+ * @return FS_Error error id
+ */
+FS_Error buffered_file_stream_get_error(Stream* stream);
+
+#ifdef __cplusplus
+}
+#endif

lib/toolbox/stream/stream_cache.c

@@ -0,0 +1,71 @@
+#include "stream_cache.h"
+
+#define STREAM_CACHE_MAX_SIZE 1024U
+
+struct StreamCache {
+    uint8_t data[STREAM_CACHE_MAX_SIZE];
+    size_t data_size;
+    size_t position;
+};
+
+StreamCache* stream_cache_alloc() {
+    StreamCache* cache = malloc(sizeof(StreamCache));
+    cache->data_size = 0;
+    cache->position = 0;
+    return cache;
+}
+void stream_cache_free(StreamCache* cache) {
+    furi_assert(cache);
+    cache->data_size = 0;
+    cache->position = 0;
+    free(cache);
+}
+
+void stream_cache_drop(StreamCache* cache) {
+    cache->data_size = 0;
+    cache->position = 0;
+}
+
+bool stream_cache_at_end(StreamCache* cache) {
+    furi_assert(cache->data_size >= cache->position);
+    return cache->data_size == cache->position;
+}
+
+size_t stream_cache_size(StreamCache* cache) {
+    return cache->data_size;
+}
+
+size_t stream_cache_pos(StreamCache* cache) {
+    return cache->position;
+}
+
+size_t stream_cache_fill(StreamCache* cache, Stream* stream) {
+    const size_t size_read = stream_read(stream, cache->data, STREAM_CACHE_MAX_SIZE);
+    cache->data_size = size_read;
+    cache->position = 0;
+    return size_read;
+}
+
+size_t stream_cache_read(StreamCache* cache, uint8_t* data, size_t size) {
+    furi_assert(cache->data_size >= cache->position);
+    const size_t size_read = MIN(size, cache->data_size - cache->position);
+    if(size_read > 0) {
+        memcpy(data, cache->data + cache->position, size_read);
+        cache->position += size_read;
+    }
+    return size_read;
+}
+
+int32_t stream_cache_seek(StreamCache* cache, int32_t offset) {
+    furi_assert(cache->data_size >= cache->position);
+    int32_t actual_offset = 0;
+
+    if(offset > 0) {
+        actual_offset = MIN(cache->data_size - cache->position, (size_t)offset);
+    } else if(offset < 0) {
+        actual_offset = -MIN(cache->position, (size_t)abs(offset));
+    }
+
+    cache->position += actual_offset;
+    return actual_offset;
+}

lib/toolbox/stream/stream_cache.h

@@ -0,0 +1,77 @@
+#pragma once
+
+#include "stream.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct StreamCache StreamCache;
+
+/**
+ * Allocate stream cache.
+ * @return StreamCache* pointer to a StreamCache instance
+ */
+StreamCache* stream_cache_alloc();
+
+/**
+ * Free stream cache.
+ * @param cache Pointer to a StreamCache instance
+ */
+void stream_cache_free(StreamCache* cache);
+
+/**
+ * Drop the cache contents and set it to initial state.
+ * @param cache Pointer to a StreamCache instance
+ */
+void stream_cache_drop(StreamCache* cache);
+
+/**
+ * Determine if the internal cursor is at end the end of cached data.
+ * @param cache Pointer to a StreamCache instance
+ * @return True if cursor is at end, otherwise false.
+ */
+bool stream_cache_at_end(StreamCache* cache);
+
+/**
+ * Get the current size of cached data.
+ * @param cache Pointer to a StreamCache instance
+ * @return Size of cached data.
+ */
+size_t stream_cache_size(StreamCache* cache);
+
+/**
+ * Get the internal cursor position.
+ * @param cache Pointer to a StreamCache instance
+ * @return Cursor position inside the cache.
+ */
+size_t stream_cache_pos(StreamCache* cache);
+
+/**
+ * Load the cache with new data from a stream.
+ * @param cache Pointer to a StreamCache instance
+ * @param stream Pointer to a Stream instance
+ * @return Size of newly cached data.
+ */
+size_t stream_cache_fill(StreamCache* cache, Stream* stream);
+
+/**
+ * Read cached data and advance the internal cursor.
+ * @param cache Pointer to a StreamCache instance.
+ * @param data Pointer to a data buffer. Must be initialized.
+ * @param size Maximum size in bytes to read from the cache.
+ * @return Actual size that was read.
+ */
+size_t stream_cache_read(StreamCache* cache, uint8_t* data, size_t size);
+
+/**
+ * Move the internal cursor relatively to its current position.
+ * @param cache Pointer to a StreamCache instance.
+ * @param offset Cursor offset.
+ * @return Actual cursor offset. Equal to offset parameter on hit.
+ */
+int32_t stream_cache_seek(StreamCache* cache, int32_t offset);
+
+#ifdef __cplusplus
+}
+#endif