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A bit additional commenting and sanity checking in PCM provider.

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Originally committed to SVN as r2234.
This commit is contained in:
Niels Martin Hansen 2008-07-04 11:37:45 +00:00
parent a1574d0a5f
commit 0d56463aa4
1 changed files with 16 additions and 5 deletions
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21
aegisub/audio_provider_pcm.cpp
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@ -167,15 +167,24 @@ char * PCMAudioProvider::EnsureRangeAccessible(int64_t range_start, int64_t rang
// 256 MB
mapping_length = 0x10000000;
#endif
if (mapping_length > file_size) mapping_length = (size_t)(file_size - mapping_start);
// Make sure to always make a mapping at least as large as the requested range
if (mapping_length < range_length)
mapping_length = range_length;
// But also make sure we don't try to make a mapping larger than the file
if (mapping_length > file_size)
mapping_length = (size_t)(file_size - mapping_start);
// We already checked that the requested range doesn't extend over the end of the file
// Hopefully this should ensure that small files are always mapped in their entirety
#ifdef _WINDOWS
LARGE_INTEGER mapping_start_li;
mapping_start_li.QuadPart = mapping_start;
current_mapping = MapViewOfFile(
file_mapping,
FILE_MAP_READ,
mapping_start >> 32, mapping_start & 0xFFFFFFFF,
mapping_length);
file_mapping, // Mapping handle
FILE_MAP_READ, // Access type
mapping_start_li.HighPart, // Offset high-part
mapping_start_li.LowPart, // Offset low-part
mapping_length); // Length of view
#else
current_mapping = mmap(0, mapping_length, PROT_READ, MAP_PRIVATE, file_handle, mapping_start);
#endif
@ -188,8 +197,10 @@ char * PCMAudioProvider::EnsureRangeAccessible(int64_t range_start, int64_t rang
assert(range_start >= mapping_start);
// Difference between actual current mapping start and requested range start
ptrdiff_t rel_ofs = (ptrdiff_t)(range_start - mapping_start);
// Calculate a pointer into current mapping for the requested range
return ((char*)current_mapping) + rel_ofs;
}