From 48fa7b7dc0d48c0ecb2e778419c2f7bb5c8cff3a Mon Sep 17 00:00:00 2001
From: bnnm <bananaman255@gmail.com>
Date: Sat, 14 Jan 2017 01:37:53 +0100
Subject: [PATCH] Added a few helper functions

- open_stream_ext: opens a streamfile based on the filename + ext
- find_chunk_be/le: finds chunk_offset in chunked headers
---
 src/streamfile.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/streamfile.h |  5 +++++
 2 files changed, 58 insertions(+)

diff --git a/src/streamfile.c b/src/streamfile.c
index 354eebc7..4399e9d8 100644
--- a/src/streamfile.c
+++ b/src/streamfile.c
@@ -273,6 +273,18 @@ size_t get_streamfile_dos_line(int dst_length, char * dst, off_t offset,
 }
 
 
+/**
+ * Opens an stream using the base streamFile name plus a new extension (ex. for headers in a separate file)
+ */
+STREAMFILE * open_stream_ext(STREAMFILE *streamFile, const char * ext) {
+    char filename_ext[PATH_LIMIT];
+
+    streamFile->get_name(streamFile,filename_ext,sizeof(filename_ext));
+    strcpy(filename_ext + strlen(filename_ext) - strlen(filename_extension(filename_ext)), ext);
+
+    return streamFile->open(streamFile,filename_ext,STREAMFILE_DEFAULT_BUFFER_SIZE);
+}
+
 /**
  * open file containing decryption keys and copy to buffer
  * tries combinations of keynames based on the original filename
@@ -419,3 +431,44 @@ int check_extensions(STREAMFILE *streamFile, const char * cmp_exts) {
 
     return 0;
 }
+
+
+/**
+ * Find a chunk starting from an offset, and save its offset/size (if not NULL), with offset after id/size.
+ * Works for chunked headers in the form of "chunk_id chunk_size (data)"xN  (ex. RIFF).
+ * The start_offset should be the first actual chunk (not "RIFF" or "WAVE" but "fmt ").
+ * "full_chunk_size" signals chunk_size includes 4+4+data.
+ *
+ * returns 0 on failure
+ */
+static int find_chunk(STREAMFILE *streamFile, uint32_t chunk_id, off_t start_offset, int full_chunk_size, int size_big_endian, off_t *out_chunk_offset, size_t *out_chunk_size);
+int find_chunk_be(STREAMFILE *streamFile, uint32_t chunk_id, off_t start_offset, int full_chunk_size, off_t *out_chunk_offset, size_t *out_chunk_size) {
+    return find_chunk(streamFile, chunk_id, start_offset, full_chunk_size, 1, out_chunk_offset, out_chunk_size);
+}
+int find_chunk_le(STREAMFILE *streamFile, uint32_t chunk_id, off_t start_offset, int full_chunk_size, off_t *out_chunk_offset, size_t *out_chunk_size) {
+    return find_chunk(streamFile, chunk_id, start_offset, full_chunk_size, 0, out_chunk_offset, out_chunk_size);
+}
+int find_chunk(STREAMFILE *streamFile, uint32_t chunk_id, off_t start_offset, int full_chunk_size, int size_big_endian, off_t *out_chunk_offset, size_t *out_chunk_size) {
+    size_t filesize;
+    off_t current_chunk = start_offset;
+
+    filesize = get_streamfile_size(streamFile);
+    /* read chunks */
+    while (current_chunk < filesize) {
+        uint32_t chunk_type = read_32bitBE(current_chunk,streamFile);
+        off_t chunk_size = size_big_endian ?
+                read_32bitBE(current_chunk+4,streamFile) :
+                read_32bitLE(current_chunk+4,streamFile);
+
+        if (chunk_type == chunk_id) {
+            if (out_chunk_offset) *out_chunk_offset = current_chunk+8;
+            if (out_chunk_size) *out_chunk_size = chunk_size;
+            return 1;
+        }
+
+        current_chunk += full_chunk_size ? chunk_size : 4+4+chunk_size;
+    }
+
+    return 0;
+}
+
diff --git a/src/streamfile.h b/src/streamfile.h
index 1127c995..5ad1f3a6 100644
--- a/src/streamfile.h
+++ b/src/streamfile.h
@@ -148,10 +148,15 @@ static inline STREAMFILE * open_stdio_streamfile(const char * const filename) {
 
 size_t get_streamfile_dos_line(int dst_length, char * dst, off_t offset, STREAMFILE * infile, int *line_done_ptr);
 
+STREAMFILE * open_stream_ext(STREAMFILE *streamFile, const char * ext);
+
 int read_key_file(uint8_t * buf, size_t bufsize, STREAMFILE *streamFile);
 
 int read_pos_file(uint8_t * buf, size_t bufsize, STREAMFILE *streamFile);
 
 int check_extensions(STREAMFILE *streamFile, const char * cmp_exts);
 
+int find_chunk_be(STREAMFILE *streamFile, uint32_t chunk_id, off_t start_offset, int full_chunk_size, off_t *out_chunk_offset, size_t *out_chunk_size);
+int find_chunk_le(STREAMFILE *streamFile, uint32_t chunk_id, off_t start_offset, int full_chunk_size, off_t *out_chunk_offset, size_t *out_chunk_size);
+
 #endif