Bug 1197377 - Read callgraph.txt line by line to avoid string size limits, r=terrence

--HG--
extra : rebase_source : b4871bc26ae32c6f93c0321910b19ff7658408d2
extra : amend_source : a9f287c617a613b53ff551263870b6ed5a003e84
extra : source : 452eaaf88ba8383dbe70b7f48e80ffcf5ebd4c6e

js/src/devtools/rootAnalysis/loadCallgraph.js

@@ -74,8 +74,9 @@ function loadCallgraph(file)
     var suppressedFieldCalls = {};
     var resolvedFunctions = {};
 
-    var textLines = snarf(file).split('\n');
-    for (var line of textLines) {
+    for (var line of readFileLines_gen(file)) {
+        line = line.replace(/\n/, "");
+
         var match;
         if (match = line.charAt(0) == "#" && /^\#(\d+) (.*)/.exec(line)) {
             assert(functionNames.length == match[1]);

js/src/devtools/rootAnalysis/utility.js

@@ -145,3 +145,32 @@ function xdbLibrary()
         free_string: lib.declare("xdb_free", ctypes.default_abi, ctypes.void_t, ctypes.char.ptr)
     };
 }
+
+function cLibrary()
+{
+    var lib;
+    try {
+        lib = ctypes.open("libc.so.6");
+    } catch(e) {
+        lib = ctypes.open("libc.so");
+    }
+
+    return {
+        fopen: lib.declare("fopen", ctypes.default_abi, ctypes.void_t.ptr, ctypes.char.ptr, ctypes.char.ptr),
+        getline: lib.declare("getline", ctypes.default_abi, ctypes.ssize_t, ctypes.char.ptr.ptr, ctypes.size_t.ptr, ctypes.void_t.ptr),
+        fclose: lib.declare("fopen", ctypes.default_abi, ctypes.int, ctypes.void_t.ptr),
+        setvbuf: lib.declare("setvbuf", ctypes.default_abi, ctypes.int, ctypes.void_t.ptr, ctypes.char.ptr, ctypes.int, ctypes.size_t),
+    };
+}
+
+function* readFileLines_gen(filename)
+{
+  var libc = cLibrary();
+  var linebuf = ctypes.char.array(4096)();
+  var bufsize = ctypes.size_t(4096);
+  var fp = libc.fopen(filename, "r");
+  var bufp = ctypes.char.ptr(linebuf.addressOfElement(0));
+  while (libc.getline(bufp.address(), bufsize.address(), fp) > 0)
+    yield bufp.readString();
+  libc.fclose(fp);
+}