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Extended MemoryMappedFile to allow loading of file subsections.

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This commit is contained in:
jules 2013-02-17 22:38:25 +00:00
parent 1e7ea748ca
commit e6d817d20d
4 changed files with 67 additions and 23 deletions
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13
modules/juce_core/files/juce_File.cpp
View file

@ -881,6 +881,19 @@ File File::createTempFile (const String& fileNameEnding)
return tempFile;
}
//==============================================================================
MemoryMappedFile::MemoryMappedFile (const File& file, MemoryMappedFile::AccessMode mode)
: address (nullptr), range (0, file.getSize()), fileHandle (0)
{
openInternal (file, mode);
}
MemoryMappedFile::MemoryMappedFile (const File& file, const Range<int64>& fileRange, AccessMode mode)
: address (nullptr), range (fileRange.getIntersectionWith (Range<int64> (0, file.getSize()))), fileHandle (0)
{
openInternal (file, mode);
}
//==============================================================================
#if JUCE_UNIT_TESTS

28
modules/juce_core/files/juce_MemoryMappedFile.h
View file

@ -57,6 +57,26 @@ public:
*/
MemoryMappedFile (const File& file, AccessMode mode);
/** Opens a section of a file and maps it to an area of virtual memory.
The file should already exist, and should already be the size that you want to work with
when you call this. If the file is resized after being opened, the behaviour is undefined.
If the file exists and the operation succeeds, the getData() and getSize() methods will
return the location and size of the data that can be read or written. Note that the entire
file is not read into memory immediately - the OS simply creates a virtual mapping, which
will lazily pull the data into memory when blocks are accessed.
If the file can't be opened for some reason, the getData() method will return a null pointer.
NOTE: the start of the actual range used may be rounded-down to a multiple of the OS's page-size,
so do not assume that the mapped memory will begin at exactly the position you requested - always
use getRange() to check the actual range that is being used.
*/
MemoryMappedFile (const File& file,
const Range<int64>& fileRange,
AccessMode mode);
/** Destructor. */
~MemoryMappedFile();
@ -68,13 +88,15 @@ public:
/** Returns the number of bytes of data that are available for reading or writing.
This will normally be the size of the file.
*/
size_t getSize() const noexcept { return length; }
size_t getSize() const noexcept { return (size_t) range.getLength(); }
/** Returns the section of the file at which the mapped memory represents. */
Range<int64> getRange() const noexcept { return range; }
private:
//==============================================================================
void* address;
size_t length;
Range<int64> range;
#if JUCE_WINDOWS
void* fileHandle;
@ -82,6 +104,8 @@ private:
int fileHandle;
#endif
void openInternal (const File&, AccessMode);
JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (MemoryMappedFile)
};

25
modules/juce_core/native/juce_posix_SharedCode.h
View file

@ -546,36 +546,37 @@ String SystemStats::getEnvironmentVariable (const String& name, const String& de
}
//==============================================================================
MemoryMappedFile::MemoryMappedFile (const File& file, MemoryMappedFile::AccessMode mode)
: address (nullptr),
length (0),
fileHandle (0)
void MemoryMappedFile::openInternal (const File& file, AccessMode mode)
{
jassert (mode == readOnly || mode == readWrite);
if (range.getStart() > 0)
{
const long pageSize = sysconf (_SC_PAGE_SIZE);
range.setStart (range.getStart() - (range.getStart() % pageSize));
}
fileHandle = open (file.getFullPathName().toUTF8(),
mode == readWrite ? (O_CREAT + O_RDWR) : O_RDONLY, 00644);
if (fileHandle != -1)
{
const int64 fileSize = file.getSize();
void* m = mmap (0, (size_t) fileSize,
void* m = mmap (0, (size_t) range.getLength(),
mode == readWrite ? (PROT_READ | PROT_WRITE) : PROT_READ,
MAP_SHARED, fileHandle, 0);
MAP_SHARED, fileHandle,
(off_t) range.getStart());
if (m != MAP_FAILED)
{
address = m;
length = (size_t) fileSize;
}
else
range = Range<int64>();
}
}
MemoryMappedFile::~MemoryMappedFile()
{
if (address != nullptr)
munmap (address, length);
munmap (address, range.getLength());
if (fileHandle != 0)
close (fileHandle);

24
modules/juce_core/native/juce_win32_Files.cpp
View file

@ -310,13 +310,18 @@ Result FileOutputStream::truncate()
}
//==============================================================================
MemoryMappedFile::MemoryMappedFile (const File& file, MemoryMappedFile::AccessMode mode)
: address (nullptr),
length (0),
fileHandle (nullptr)
void MemoryMappedFile::openInternal (const File& file, AccessMode mode)
{
jassert (mode == readOnly || mode == readWrite);
if (range.getStart() > 0)
{
SYSTEM_INFO systemInfo;
GetNativeSystemInfo (&systemInfo);
range.setStart (range.getStart() - (range.getStart() % systemInfo.dwAllocationGranularity));
}
DWORD accessMode = GENERIC_READ, createType = OPEN_EXISTING;
DWORD protect = PAGE_READONLY, access = FILE_MAP_READ;
@ -334,15 +339,16 @@ MemoryMappedFile::MemoryMappedFile (const File& file, MemoryMappedFile::AccessMo
if (h != INVALID_HANDLE_VALUE)
{
fileHandle = (void*) h;
const int64 fileSize = file.getSize();
HANDLE mappingHandle = CreateFileMapping (h, 0, protect, (DWORD) (fileSize >> 32), (DWORD) fileSize, 0);
HANDLE mappingHandle = CreateFileMapping (h, 0, protect, (DWORD) (range.getEnd() >> 32), (DWORD) range.getEnd(), 0);
if (mappingHandle != 0)
{
address = MapViewOfFile (mappingHandle, access, 0, 0, (SIZE_T) fileSize);
address = MapViewOfFile (mappingHandle, access, (DWORD) (range.getStart() >> 32),
(DWORD) range.getStart(), (SIZE_T) range.getLength());
if (address != nullptr)
length = (size_t) fileSize;
if (address == nullptr)
range = Range<int64>();
CloseHandle (mappingHandle);
}