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Add buffer comments

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This commit is contained in:
bnnm 2019-11-03 17:57:07 +01:00
parent e06e2f2bb2
commit b2e3058072
2 changed files with 12 additions and 4 deletions
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10
src/streamfile.h
View File

@ -45,8 +45,6 @@
#define fseeko fseek
#endif
#define STREAMFILE_DEFAULT_BUFFER_SIZE 0x8000
#ifndef DIR_SEPARATOR
#if defined (_WIN32) || defined (WIN32)
#define DIR_SEPARATOR '\\'
@ -55,6 +53,14 @@
#endif
#endif
/* Streamfiles normally use an internal buffer to increase performance, configurable
* but usually of this size. Lower increases the number of freads/system calls (slower).
* However some formats need to jump around causing more buffer trashing than usual,
* higher may needlessly read data that may be going to be trashed.
*
* Value can be adjusted freely but 8k is a good enough compromise. */
#define STREAMFILE_DEFAULT_BUFFER_SIZE 0x8000
/* struct representing a file with callbacks. Code should use STREAMFILEs and not std C functions
* to do file operations, as plugins may need to provide their own callbacks.
* Reads from arbitrary offsets, meaning internally may need fseek equivalents during reads. */

6
src/vgmstream.c
View File

@ -2819,7 +2819,8 @@ int vgmstream_open_stream(VGMSTREAM * vgmstream, STREAMFILE *streamFile, off_t s
}
/* if blocked layout (implicit) use multiple streamfiles; using only one leads to
* lots of buffer-trashing, with all the jumping around in the block layout */
* lots of buffer-trashing, with all the jumping around in the block layout
* (this increases total of data read but still seems faster) */
if (vgmstream->layout_type != layout_none && vgmstream->layout_type != layout_interleave) {
use_streamfile_per_channel = 1;
}
@ -2860,7 +2861,8 @@ int vgmstream_open_stream(VGMSTREAM * vgmstream, STREAMFILE *streamFile, off_t s
offset = start_offset + vgmstream->interleave_block_size*ch;
}
/* open new one if needed */
/* open new one if needed, useful to avoid jumping around when each channel data is too apart
* (don't use when data is close as it'd make buffers read the full file multiple times) */
if (use_streamfile_per_channel) {
file = open_streamfile(streamFile,filename);
if (!file) goto fail;