1 files changed, 194 insertions, 0 deletions
diff --git a/tensorflow/core/lib/strings/strcat.cc b/tensorflow/core/lib/strings/strcat.cc
new file mode 100644
index 0000000000..e564b9eb73
--- /dev/null
+++ b/tensorflow/core/lib/strings/strcat.cc
@@ -0,0 +1,194 @@
+#include "tensorflow/core/lib/strings/strcat.h"
+
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "tensorflow/core/platform/logging.h"
+#include "tensorflow/core/lib/gtl/stl_util.h"
+
+namespace tensorflow {
+namespace strings {
+
+AlphaNum gEmptyAlphaNum("");
+
+AlphaNum::AlphaNum(Hex hex) {
+  char *const end = &digits_[kFastToBufferSize];
+  char *writer = end;
+  uint64 value = hex.value;
+  uint64 width = hex.spec;
+  // We accomplish minimum width by OR'ing in 0x10000 to the user's value,
+  // where 0x10000 is the smallest hex number that is as wide as the user
+  // asked for.
+  uint64 mask = ((static_cast<uint64>(1) << (width - 1) * 4)) | value;
+  static const char hexdigits[] = "0123456789abcdef";
+  do {
+    *--writer = hexdigits[value & 0xF];
+    value >>= 4;
+    mask >>= 4;
+  } while (mask != 0);
+  piece_.set(writer, end - writer);
+}
+
+// ----------------------------------------------------------------------
+// StrCat()
+//    This merges the given strings or integers, with no delimiter.  This
+//    is designed to be the fastest possible way to construct a string out
+//    of a mix of raw C strings, StringPieces, strings, and integer values.
+// ----------------------------------------------------------------------
+
+// Append is merely a version of memcpy that returns the address of the byte
+// after the area just overwritten.  It comes in multiple flavors to minimize
+// call overhead.
+static char *Append1(char *out, const AlphaNum &x) {
+  memcpy(out, x.data(), x.size());
+  return out + x.size();
+}
+
+static char *Append2(char *out, const AlphaNum &x1, const AlphaNum &x2) {
+  memcpy(out, x1.data(), x1.size());
+  out += x1.size();
+
+  memcpy(out, x2.data(), x2.size());
+  return out + x2.size();
+}
+
+static char *Append4(char *out, const AlphaNum &x1, const AlphaNum &x2,
+                     const AlphaNum &x3, const AlphaNum &x4) {
+  memcpy(out, x1.data(), x1.size());
+  out += x1.size();
+
+  memcpy(out, x2.data(), x2.size());
+  out += x2.size();
+
+  memcpy(out, x3.data(), x3.size());
+  out += x3.size();
+
+  memcpy(out, x4.data(), x4.size());
+  return out + x4.size();
+}
+
+string StrCat(const AlphaNum &a, const AlphaNum &b) {
+  string result;
+  gtl::STLStringResizeUninitialized(&result, a.size() + b.size());
+  char *const begin = &*result.begin();
+  char *out = Append2(begin, a, b);
+  DCHECK_EQ(out, begin + result.size());
+  return result;
+}
+
+string StrCat(const AlphaNum &a, const AlphaNum &b, const AlphaNum &c) {
+  string result;
+  gtl::STLStringResizeUninitialized(&result, a.size() + b.size() + c.size());
+  char *const begin = &*result.begin();
+  char *out = Append2(begin, a, b);
+  out = Append1(out, c);
+  DCHECK_EQ(out, begin + result.size());
+  return result;
+}
+
+string StrCat(const AlphaNum &a, const AlphaNum &b, const AlphaNum &c,
+              const AlphaNum &d) {
+  string result;
+  gtl::STLStringResizeUninitialized(&result,
+                                    a.size() + b.size() + c.size() + d.size());
+  char *const begin = &*result.begin();
+  char *out = Append4(begin, a, b, c, d);
+  DCHECK_EQ(out, begin + result.size());
+  return result;
+}
+
+namespace internal {
+
+// Do not call directly - these are not part of the public API.
+string CatPieces(std::initializer_list<StringPiece> pieces) {
+  string result;
+  size_t total_size = 0;
+  for (const StringPiece piece : pieces) total_size += piece.size();
+  gtl::STLStringResizeUninitialized(&result, total_size);
+
+  char *const begin = &*result.begin();
+  char *out = begin;
+  for (const StringPiece piece : pieces) {
+    const size_t this_size = piece.size();
+    memcpy(out, piece.data(), this_size);
+    out += this_size;
+  }
+  DCHECK_EQ(out, begin + result.size());
+  return result;
+}
+
+// It's possible to call StrAppend with a StringPiece that is itself a fragment
+// of the string we're appending to.  However the results of this are random.
+// Therefore, check for this in debug mode.  Use unsigned math so we only have
+// to do one comparison.
+#define DCHECK_NO_OVERLAP(dest, src) \
+  DCHECK_GE(uintptr_t((src).data() - (dest).data()), uintptr_t((dest).size()))
+
+void AppendPieces(string *result, std::initializer_list<StringPiece> pieces) {
+  size_t old_size = result->size();
+  size_t total_size = old_size;
+  for (const StringPiece piece : pieces) {
+    DCHECK_NO_OVERLAP(*result, piece);
+    total_size += piece.size();
+  }
+  gtl::STLStringResizeUninitialized(result, total_size);
+
+  char *const begin = &*result->begin();
+  char *out = begin + old_size;
+  for (const StringPiece piece : pieces) {
+    const size_t this_size = piece.size();
+    memcpy(out, piece.data(), this_size);
+    out += this_size;
+  }
+  DCHECK_EQ(out, begin + result->size());
+}
+
+}  // namespace internal
+
+void StrAppend(string *result, const AlphaNum &a) {
+  DCHECK_NO_OVERLAP(*result, a);
+  result->append(a.data(), a.size());
+}
+
+void StrAppend(string *result, const AlphaNum &a, const AlphaNum &b) {
+  DCHECK_NO_OVERLAP(*result, a);
+  DCHECK_NO_OVERLAP(*result, b);
+  string::size_type old_size = result->size();
+  gtl::STLStringResizeUninitialized(result, old_size + a.size() + b.size());
+  char *const begin = &*result->begin();
+  char *out = Append2(begin + old_size, a, b);
+  DCHECK_EQ(out, begin + result->size());
+}
+
+void StrAppend(string *result, const AlphaNum &a, const AlphaNum &b,
+               const AlphaNum &c) {
+  DCHECK_NO_OVERLAP(*result, a);
+  DCHECK_NO_OVERLAP(*result, b);
+  DCHECK_NO_OVERLAP(*result, c);
+  string::size_type old_size = result->size();
+  gtl::STLStringResizeUninitialized(result,
+                                    old_size + a.size() + b.size() + c.size());
+  char *const begin = &*result->begin();
+  char *out = Append2(begin + old_size, a, b);
+  out = Append1(out, c);
+  DCHECK_EQ(out, begin + result->size());
+}
+
+void StrAppend(string *result, const AlphaNum &a, const AlphaNum &b,
+               const AlphaNum &c, const AlphaNum &d) {
+  DCHECK_NO_OVERLAP(*result, a);
+  DCHECK_NO_OVERLAP(*result, b);
+  DCHECK_NO_OVERLAP(*result, c);
+  DCHECK_NO_OVERLAP(*result, d);
+  string::size_type old_size = result->size();
+  gtl::STLStringResizeUninitialized(
+      result, old_size + a.size() + b.size() + c.size() + d.size());
+  char *const begin = &*result->begin();
+  char *out = Append4(begin + old_size, a, b, c, d);
+  DCHECK_EQ(out, begin + result->size());
+}
+
+}  // namespace strings
+}  // namespace tensorflow