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"
@@ -17,6 +20,60 @@
 
 namespace content {
 
+// Takes "ownership" of the file descriptor, and will close() it.
+class SkFileDescriptorStream : public SkStream {
+ public:
+  SkFileDescriptorStream(int fd) : memory_(NULL), offset_(0), length_(0) {
+    struct stat st;
+    if (fstat(fd, &st)) {
+      DCHECK(!HANDLE_EINTR(close(fd)));

[piman, 2013/03/18 19:49:14]

no side effects inside of DCHECK please.

+      return;
+    }
+
+    void* memory = mmap(NULL, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
+    DCHECK(!HANDLE_EINTR(close(fd)));

[piman, 2013/03/18 19:49:14]

no side effects inside of DCHECK please.

+    if (memory == MAP_FAILED)
+      return;
+
+    memory_ = reinterpret_cast<uint8_t*>(memory);
+    length_ = st.st_size;
+  }
+
+  virtual ~SkFileDescriptorStream() {
+    if (memory_)
+      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_;
+};
+
 FontConfigIPC::FontConfigIPC(int fd)
     : fd_(fd) {
 }
@@ -97,7 +154,7 @@
     return NULL;
   }
 
-  return new SkFDStream(result_fd, true);
+  return new SkFileDescriptorStream(result_fd);

[piman, 2013/03/18 19:49:14]

If the map failed inside of the constructor, shouldn't we return NULL here?

[reed1, 2013/03/18 20:15:41]

Done.

 }
 
 }  // namespace content