Small cleanup StrCat related number formatting

- Resolve inconsistency in return values (pointer to start vs end of buffer)
- Instead, return the number of chars written as this turns out to be most useful to callers
- Removes the need for redundant strlen calls.

PiperOrigin-RevId: 190085812

1 files changed, 28 insertions, 21 deletions

diff --git a/tensorflow/core/lib/strings/numbers.cc b/tensorflow/core/lib/strings/numbers.cc
index f5822fad8e..516decc3c0 100644
--- a/tensorflow/core/lib/strings/numbers.cc
+++ b/tensorflow/core/lib/strings/numbers.cc
@@ -106,19 +106,22 @@ T locale_independent_strtonum(const char* str, const char** endptr) {
 
 namespace strings {
 
-char* FastInt32ToBufferLeft(int32 i, char* buffer) {
+size_t FastInt32ToBufferLeft(int32 i, char* buffer) {
   uint32 u = i;
+  size_t length = 0;
   if (i < 0) {
     *buffer++ = '-';
+    ++length;
     // We need to do the negation in modular (i.e., "unsigned")
     // arithmetic; MSVC++ apparently warns for plain "-u", so
     // we write the equivalent expression "0 - u" instead.
     u = 0 - u;
   }
-  return FastUInt32ToBufferLeft(u, buffer);
+  length += FastUInt32ToBufferLeft(u, buffer);
+  return length;
 }
 
-char* FastUInt32ToBufferLeft(uint32 i, char* buffer) {
+size_t FastUInt32ToBufferLeft(uint32 i, char* buffer) {
   char* start = buffer;
   do {
     *buffer++ = ((i % 10) + '0');
@@ -126,19 +129,22 @@ char* FastUInt32ToBufferLeft(uint32 i, char* buffer) {
   } while (i > 0);
   *buffer = 0;
   std::reverse(start, buffer);
-  return buffer;
+  return buffer - start;
 }
 
-char* FastInt64ToBufferLeft(int64 i, char* buffer) {
+size_t FastInt64ToBufferLeft(int64 i, char* buffer) {
   uint64 u = i;
+  size_t length = 0;
   if (i < 0) {
     *buffer++ = '-';
+    ++length;
     u = 0 - u;
   }
-  return FastUInt64ToBufferLeft(u, buffer);
+  length += FastUInt64ToBufferLeft(u, buffer);
+  return length;
 }
 
-char* FastUInt64ToBufferLeft(uint64 i, char* buffer) {
+size_t FastUInt64ToBufferLeft(uint64 i, char* buffer) {
   char* start = buffer;
   do {
     *buffer++ = ((i % 10) + '0');
@@ -146,19 +152,18 @@ char* FastUInt64ToBufferLeft(uint64 i, char* buffer) {
   } while (i > 0);
   *buffer = 0;
   std::reverse(start, buffer);
-  return buffer;
+  return buffer - start;
 }
 
 static const double kDoublePrecisionCheckMax = DBL_MAX / 1.000000000000001;
 
-char* DoubleToBuffer(double value, char* buffer) {
+size_t DoubleToBuffer(double value, char* buffer) {
   // DBL_DIG is 15 for IEEE-754 doubles, which are used on almost all
   // platforms these days.  Just in case some system exists where DBL_DIG
   // is significantly larger -- and risks overflowing our buffer -- we have
   // this assert.
   static_assert(DBL_DIG < 20, "DBL_DIG is too big");
 
-  bool full_precision_needed = true;
   if (std::abs(value) <= kDoublePrecisionCheckMax) {
     int snprintf_result =
         snprintf(buffer, kFastToBufferSize, "%.*g", DBL_DIG, value);
@@ -167,18 +172,20 @@ char* DoubleToBuffer(double value, char* buffer) {
     // larger than the precision we asked for.
     DCHECK(snprintf_result > 0 && snprintf_result < kFastToBufferSize);
 
-    full_precision_needed =
-        locale_independent_strtonum<double>(buffer, nullptr) != value;
+    if (locale_independent_strtonum<double>(buffer, nullptr) == value) {
+      // Round-tripping the string to double works; we're done.
+      return snprintf_result;
+    }
+    // else: full precision formatting needed. Fall through.
   }
 
-  if (full_precision_needed) {
-    int snprintf_result =
-        snprintf(buffer, kFastToBufferSize, "%.*g", DBL_DIG + 2, value);
+  int snprintf_result =
+      snprintf(buffer, kFastToBufferSize, "%.*g", DBL_DIG + 2, value);
 
-    // Should never overflow; see above.
-    DCHECK(snprintf_result > 0 && snprintf_result < kFastToBufferSize);
-  }
-  return buffer;
+  // Should never overflow; see above.
+  DCHECK(snprintf_result > 0 && snprintf_result < kFastToBufferSize);
+
+  return snprintf_result;
 }
 
 namespace {
@@ -325,7 +332,7 @@ bool safe_strtod(const char* str, double* value) {
   return *str != '\0' && *endptr == '\0';
 }
 
-char* FloatToBuffer(float value, char* buffer) {
+size_t FloatToBuffer(float value, char* buffer) {
   // FLT_DIG is 6 for IEEE-754 floats, which are used on almost all
   // platforms these days.  Just in case some system exists where FLT_DIG
   // is significantly larger -- and risks overflowing our buffer -- we have
@@ -347,7 +354,7 @@ char* FloatToBuffer(float value, char* buffer) {
     // Should never overflow; see above.
     DCHECK(snprintf_result > 0 && snprintf_result < kFastToBufferSize);
   }
-  return buffer;
+  return snprintf_result;
 }
 
 string FpToString(Fprint fp) {