Support read/write memory-mapped files.
See also: chromium-dev thread "Support for Writable Memory Mapped Files", specifically the last few messages starting with "And... we're back!".
BUG=546019
Review-Url: https://codereview.chromium.org/1798203002
Cr-Commit-Position: refs/heads/master@{#394868}
diff --git a/base/files/memory_mapped_file_posix.cc b/base/files/memory_mapped_file_posix.cc
index 1067fdc9..4899cf0cd 100644
--- a/base/files/memory_mapped_file_posix.cc
+++ b/base/files/memory_mapped_file_posix.cc
@@ -21,7 +21,8 @@
#if !defined(OS_NACL)
bool MemoryMappedFile::MapFileRegionToMemory(
- const MemoryMappedFile::Region& region) {
+ const MemoryMappedFile::Region& region,
+ Access access) {
ThreadRestrictions::AssertIOAllowed();
off_t map_start = 0;
@@ -65,7 +66,23 @@
length_ = static_cast<size_t>(region.size);
}
- data_ = static_cast<uint8_t*>(mmap(NULL, map_size, PROT_READ, MAP_SHARED,
+ int flags = 0;
+ switch (access) {
+ case READ_ONLY:
+ flags |= PROT_READ;
+ break;
+ case READ_WRITE:
+ flags |= PROT_READ | PROT_WRITE;
+ break;
+ case READ_WRITE_EXTEND:
+ // POSIX won't auto-extend the file when it is written so it must first
+ // be explicitly extended to the maximum size. Zeros will fill the new
+ // space.
+ file_.SetLength(std::max(file_.GetLength(), region.offset + region.size));
+ flags |= PROT_READ | PROT_WRITE;
+ break;
+ }
+ data_ = static_cast<uint8_t*>(mmap(NULL, map_size, flags, MAP_SHARED,
file_.GetPlatformFile(), map_start));
if (data_ == MAP_FAILED) {
DPLOG(ERROR) << "mmap " << file_.GetPlatformFile();
