mmap the opened file descriptor in the renderer process, close the fd in the browser process.

content/common/font_config_ipc_linux.cc

Index: content/common/font_config_ipc_linux.cc
===================================================================
--- content/common/font_config_ipc_linux.cc	(revision 188729)
+++ content/common/font_config_ipc_linux.cc	(working copy)
@@ -6,10 +6,13 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <sys/mman.h>
 #include <sys/socket.h>
+#include <sys/stat.h>
 #include <sys/uio.h>
 #include <unistd.h>
 
+#include "base/file_util.h"
 #include "base/pickle.h"
 #include "base/posix/unix_domain_socket_linux.h"
 #include "skia/ext/skia_utils_base.h"
@@ -17,12 +20,73 @@
 
 namespace content {
 
+// Is given a mmap'd address, and will unmap it in its destructor
+class MMapStream : public SkStream {
+ public:
+  MMapStream(const void* addr, size_t length)
+    : memory_(reinterpret_cast<const uint8_t*>(addr))
+    , offset_(0)
+    , length_(length)
+  {}
+
+  virtual ~MMapStream() {
+    munmap(const_cast<uint8_t*>(memory_), length_);
+  }
+
+  virtual bool rewind() OVERRIDE {
+    offset_ = 0;
+    return true;
+  }
+
+  virtual size_t read(void* buffer, size_t size) OVERRIDE {
+    if (!buffer && !size) {
+      // This is request for the length of the stream.
+      return length_;
+    }
+
+    size_t remaining = length_ - offset_;
+    if (size > remaining)
+      size = remaining;
+    if (buffer)
+      memcpy(buffer, memory_ + offset_, size);
+
+    offset_ += size;
+    return size;
+  }
+
+  virtual const void* getMemoryBase() OVERRIDE {
+    return memory_;
+  }
+
+ private:
+  const uint8_t* memory_;
+  size_t offset_, length_;
+};
+
+// Return a stream from the file descriptor, or NULL on failure.
+SkStream* StreamFromFD(int fd) {
+  struct stat st;
+  if (fstat(fd, &st))
+    return NULL;
+
+  void* memory = mmap(NULL, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
+  if (memory == MAP_FAILED)
+    return NULL;
+
+  return new MMapStream(memory, st.st_size);
+}
+
+void CloseFD(int fd) {
+  int err = HANDLE_EINTR(close(fd));
+  DCHECK(!err);
+}
+
 FontConfigIPC::FontConfigIPC(int fd)
     : fd_(fd) {
 }
 
 FontConfigIPC::~FontConfigIPC() {
-  close(fd_);
+  CloseFD(fd_);
 }
 
 bool FontConfigIPC::matchFamilyName(const char familyName[],
@@ -93,11 +157,14 @@
   if (!reply.ReadBool(&iter, &result) ||
       !result) {
     if (result_fd)
-      close(result_fd);
+      CloseFD(result_fd);
     return NULL;
   }
 
-  return new SkFDStream(result_fd, true);
+  SkStream* stream = StreamFromFD(result_fd);
+  CloseFD(result_fd);
+  return stream;
 }
 
 }  // namespace content
+