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//========================================================================
//
// InMemoryFile.cc
//
// Represents a file in-memory with GNU's stdio wrappers.
// NOTE as of this writing, open() depends on the glibc 'fopencookie'
// extension and is not supported on other platforms. The
// HAVE_IN_MEMORY_FILE macro is intended to reflect whether this class is
// usable.
//
// This file is licensed under the GPLv2 or later
//
// Copyright (C) 2018, 2019 Greg Knight <[email protected]>
// Copyright (C) 2020 Albert Astals Cid <[email protected]>
//
//========================================================================
#include "InMemoryFile.h"
#include <cstring>
#include <sstream>
InMemoryFile::InMemoryFile() = default;
#ifdef HAVE_IN_MEMORY_FILE_FOPENCOOKIE
ssize_t InMemoryFile::_read(char *buf, size_t sz)
{
auto toRead = std::min<size_t>(data.size() - iohead, sz);
memcpy(&buf[0], &data[iohead], toRead);
iohead += toRead;
return toRead;
}
ssize_t InMemoryFile::_write(const char *buf, size_t sz)
{
if (iohead + sz > data.size()) {
data.resize(iohead + sz);
}
memcpy(&data[iohead], buf, sz);
iohead += sz;
return sz;
}
int InMemoryFile::_seek(off64_t *offset, int whence)
{
switch (whence) {
case SEEK_SET:
iohead = (*offset);
break;
case SEEK_CUR:
iohead += (*offset);
break;
case SEEK_END:
iohead -= (*offset);
break;
}
(*offset) = std::min<off64_t>(std::max<off64_t>(iohead, 0l), data.size());
iohead = static_cast<size_t>(*offset);
return 0;
}
#endif // def HAVE_IN_MEMORY_FILE_FOPENCOOKIE
FILE *InMemoryFile::open(const char *mode)
{
#ifdef HAVE_IN_MEMORY_FILE_FOPENCOOKIE
if (fptr != nullptr) {
fprintf(stderr, "InMemoryFile: BUG: Why is this opened more than once?");
return nullptr; // maybe there's some legit reason for it, whoever comes up with one can remove this line
}
static const cookie_io_functions_t methods = {
/* .read = */ [](void *self, char *buf, size_t sz) { return ((InMemoryFile *)self)->_read(buf, sz); },
/* .write = */ [](void *self, const char *buf, size_t sz) { return ((InMemoryFile *)self)->_write(buf, sz); },
/* .seek = */ [](void *self, off64_t *offset, int whence) { return ((InMemoryFile *)self)->_seek(offset, whence); },
/* .close = */
[](void *self) {
((InMemoryFile *)self)->fptr = nullptr;
return 0;
},
};
return fptr = fopencookie(this, mode, methods);
#else
fprintf(stderr, "If you can read this, your platform does not support the features necessary to achieve your goals.");
return nullptr;
#endif
}
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