Make strlcpy available in folly

Summary:
strncpy is bad.  strlcpy is somewhat less bad.  We already had
this function, but let's move it somewhere more reasonable.

Test Plan: runtests

Reviewed By: ldbrandy@fb.com

Subscribers: trunkagent, lins, anca, folly-diffs@, yfeldblum, chalfant

FB internal diff: D2062632

Signature: t1:2062632:1431969926:cc7f7283073d0242fe8f361efac2557aa0b0a481

folly/Demangle.cpp

@@ -20,6 +20,7 @@
 #include <string.h>
 
 #include <folly/Malloc.h>
+#include <folly/String.h>
 
 #if FOLLY_HAVE_CPLUS_DEMANGLE_V3_CALLBACK
 # include <cxxabi.h>
@@ -55,21 +56,6 @@ extern "C" int cplus_demangle_v3_callback(
 
 #endif
 
-namespace {
-
-// glibc doesn't have strlcpy
-size_t my_strlcpy(char* dest, const char* src, size_t size) {
-  size_t len = strlen(src);
-  if (size != 0) {
-    size_t n = std::min(len, size - 1);  // always null terminate!
-    memcpy(dest, src, n);
-    dest[n] = '\0';
-  }
-  return len;
-}
-
-}  // namespace
-
 namespace folly {
 
 #if FOLLY_HAVE_CPLUS_DEMANGLE_V3_CALLBACK
@@ -119,7 +105,7 @@ size_t demangle(const char* name, char* out, size_t outSize) {
       demangleCallback,
       &dbuf);
   if (status == 0) {  // failed, return original
-    return my_strlcpy(out, name, outSize);
+    return folly::strlcpy(out, name, outSize);
   }
   if (outSize != 0) {
     *dbuf.dest = '\0';
@@ -134,7 +120,7 @@ fbstring demangle(const char* name) {
 }
 
 size_t demangle(const char* name, char* out, size_t outSize) {
-  return my_strlcpy(out, name, outSize);
+  return folly::strlcpy(out, name, outSize);
 }
 
 #endif

folly/String.cpp

@@ -492,6 +492,16 @@ void toLowerAscii(char* str, size_t length) {
   }
 }
 
+size_t strlcpy(char* dest, const char* const src, size_t size) {
+  size_t len = strlen(src);
+  if (size != 0) {
+    size_t n = std::min(len, size - 1);  // always null terminate!
+    memcpy(dest, src, n);
+    dest[n] = '\0';
+  }
+  return len;
+}
+
 namespace detail {
 
 size_t hexDumpLine(const void* ptr, size_t offset, size_t size,

folly/String.h

@@ -569,6 +569,9 @@ inline void toLowerAscii(MutableStringPiece str) {
   toLowerAscii(str.begin(), str.size());
 }
 
+// glibc doesn't have strlcpy
+size_t strlcpy(char* dest, const char* const src, size_t size);
+
 } // namespace folly
 
 // Hook into boost's type traits