Weed out extreme exponents in strtod.

If a decimal exponent is less than -309 return 0.0.
If a decimal exponent is greater than +324 return +infinity.

BUG=
TEST=

Review URL: http://codereview.chromium.org/3519017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5623 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

diff --git a/src/conversions.cc b/src/conversions.cc
index a7a0867..790e807 100644 (file)
--- a/src/conversions.cc
+++ b/src/conversions.cc
@@ -353,7 +353,7 @@ static double InternalStringToInt(Iterator current, EndMark end, int radix) {
 
     ASSERT(buffer_pos < kBufferSize);
     buffer[buffer_pos] = '\0';
-    Vector<char> buffer_vector(buffer, buffer_pos);
+    Vector<const char> buffer_vector(buffer, buffer_pos);
     return sign ? -Strtod(buffer_vector, 0) : Strtod(buffer_vector, 0);
   }
 
@@ -653,7 +653,7 @@ static double InternalStringToDouble(Iterator current,
   ASSERT(buffer_pos < kBufferSize);
   buffer[buffer_pos] = '\0';
 
-  double converted = Strtod(Vector<char>(buffer, buffer_pos), exponent);
+  double converted = Strtod(Vector<const char>(buffer, buffer_pos), exponent);
   return sign? -converted: converted;
 }
 

diff --git a/src/strtod.cc b/src/strtod.cc
index bfbb5db..68444fc 100644 (file)
--- a/src/strtod.cc
+++ b/src/strtod.cc
@@ -43,6 +43,14 @@ static const int kMaxExactDoubleIntegerDecimalDigits = 15;
 // 2^64 = 18446744073709551616
 // Any integer with at most 19 digits will hence fit into a 64bit datatype.
 static const int kMaxUint64DecimalDigits = 19;
+// Max double: 1.7976931348623157 x 10^308
+// Min non-zero double: 4.9406564584124654 x 10^-324
+// Any x >= 10^309 is interpreted as +infinity.
+// Any x <= 10^-324 is interpreted as 0.
+// Note that 2.5e-324 (despite being smaller than the min double) will be read
+// as non-zero (equal to the min non-zero double).
+static const int kMaxDecimalPower = 309;
+static const int kMinDecimalPower = -324;
 
 static const double exact_powers_of_ten[] = {
   1.0,  // 10^0
@@ -76,26 +84,50 @@ static const int kExactPowersOfTenSize = ARRAY_SIZE(exact_powers_of_ten);
 
 extern "C" double gay_strtod(const char* s00, const char** se);
 
-static double old_strtod(Vector<char> buffer, int exponent) {
+static double old_strtod(Vector<const char> buffer, int exponent) {
   char gay_buffer[1024];
   Vector<char> gay_buffer_vector(gay_buffer, sizeof(gay_buffer));
-  buffer.start()[buffer.length()] = '\0';
-  OS::SNPrintF(gay_buffer_vector, "%se%d", buffer.start(), exponent);
+  int pos = 0;
+  for (int i = 0; i < buffer.length(); ++i) {
+    gay_buffer_vector[pos++] = buffer[i];
+  }
+  gay_buffer_vector[pos++] = 'e';
+  if (exponent < 0) {
+    gay_buffer_vector[pos++] = '-';
+    exponent = -exponent;
+  }
+  const int kNumberOfExponentDigits = 5;
+  for (int i = kNumberOfExponentDigits - 1; i >= 0; i--) {
+    gay_buffer_vector[pos + i] = exponent % 10 + '0';
+    exponent /= 10;
+  }
+  pos += kNumberOfExponentDigits;
+  gay_buffer_vector[pos] = '\0';
   return gay_strtod(gay_buffer, NULL);
 }
 
 
-static Vector<char> TrimTrailingZeros(Vector<char> buffer) {
+static Vector<const char> TrimLeadingZeros(Vector<const char> buffer) {
+  for (int i = 0; i < buffer.length(); i++) {
+    if (buffer[i] != '0') {
+      return Vector<const char>(buffer.start() + i, buffer.length() - i);
+    }
+  }
+  return Vector<const char>(buffer.start(), 0);
+}
+
+
+static Vector<const char> TrimTrailingZeros(Vector<const char> buffer) {
   for (int i = buffer.length() - 1; i >= 0; --i) {
     if (buffer[i] != '0') {
-      return Vector<char>(buffer.start(), i + 1);
+      return Vector<const char>(buffer.start(), i + 1);
     }
   }
-  return Vector<char>(buffer.start(), 0);
+  return Vector<const char>(buffer.start(), 0);
 }
 
 
-uint64_t ReadUint64(Vector<char> buffer) {
+uint64_t ReadUint64(Vector<const char> buffer) {
   ASSERT(buffer.length() <= kMaxUint64DecimalDigits);
   uint64_t result = 0;
   for (int i = 0; i < buffer.length(); ++i) {
@@ -107,10 +139,13 @@ uint64_t ReadUint64(Vector<char> buffer) {
 }
 
 
-double Strtod(Vector<char> buffer, int exponent) {
-  Vector<char> trimmed = TrimTrailingZeros(buffer);
+double Strtod(Vector<const char> buffer, int exponent) {
+  Vector<const char> left_trimmed = TrimLeadingZeros(buffer);
+  Vector<const char> trimmed = TrimTrailingZeros(left_trimmed);
+  exponent += left_trimmed.length() - trimmed.length();
   if (trimmed.length() == 0) return 0.0;
-  exponent += buffer.length() - trimmed.length();
+  if (exponent + trimmed.length() - 1 >= kMaxDecimalPower) return V8_INFINITY;
+  if (exponent + trimmed.length() <= kMinDecimalPower) return 0.0;
   if (trimmed.length() <= kMaxExactDoubleIntegerDecimalDigits) {
     // The trimmed input fits into a double.
     // If the 10^exponent (resp. 10^-exponent) fits into a double too then we

diff --git a/src/strtod.h b/src/strtod.h
index 4d256ba..1a5a96c 100644 (file)
--- a/src/strtod.h
+++ b/src/strtod.h
@@ -33,7 +33,7 @@ namespace internal {
 
 // The buffer must only contain digits in the range [0-9]. It must not
 // contain a dot or a sign. It must not start with '0', and must not be empty.
-double Strtod(Vector<char> buffer, int exponent);
+double Strtod(Vector<const char> buffer, int exponent);
 
 } }  // namespace v8::internal
 

diff --git a/test/cctest/test-strtod.cc b/test/cctest/test-strtod.cc
index 85a7dbd..1eefb7f 100644 (file)
--- a/test/cctest/test-strtod.cc
+++ b/test/cctest/test-strtod.cc
@@ -4,30 +4,32 @@
 
 #include "v8.h"
 
-#include "platform.h"
 #include "cctest.h"
 #include "strtod.h"
 
 using namespace v8::internal;
 
-static const int kBufferSize = 100;
+static Vector<const char> StringToVector(const char* str) {
+  return Vector<const char>(str, StrLength(str));
+}
+
+
+static double StrtodChar(const char* str, int exponent) {
+  return Strtod(StringToVector(str), exponent);
+}
 
 
 TEST(Strtod) {
-  char buffer_array[kBufferSize];
-  Vector<char> buffer(buffer_array, kBufferSize);
-  Vector<char> vector;
+  Vector<const char> vector;
 
-  OS::StrNCpy(buffer, "0", kBufferSize);
-  vector = Vector<char>(buffer_array, strlen(buffer_array));
+  vector = StringToVector("0");
   CHECK_EQ(0.0, Strtod(vector, 1));
   CHECK_EQ(0.0, Strtod(vector, 2));
   CHECK_EQ(0.0, Strtod(vector, -2));
   CHECK_EQ(0.0, Strtod(vector, -999));
   CHECK_EQ(0.0, Strtod(vector, +999));
 
-  OS::StrNCpy(buffer, "1", kBufferSize);
-  vector = Vector<char>(buffer_array, strlen(buffer_array));
+  vector = StringToVector("1");
   CHECK_EQ(1.0, Strtod(vector, 0));
   CHECK_EQ(10.0, Strtod(vector, 1));
   CHECK_EQ(100.0, Strtod(vector, 2));
@@ -46,8 +48,7 @@ TEST(Strtod) {
   CHECK_EQ(1e-25, Strtod(vector, -25));
   CHECK_EQ(1e-39, Strtod(vector, -39));
 
-  OS::StrNCpy(buffer, "2", kBufferSize);
-  vector = Vector<char>(buffer_array, strlen(buffer_array));
+  vector = StringToVector("2");
   CHECK_EQ(2.0, Strtod(vector, 0));
   CHECK_EQ(20.0, Strtod(vector, 1));
   CHECK_EQ(200.0, Strtod(vector, 2));
@@ -66,8 +67,7 @@ TEST(Strtod) {
   CHECK_EQ(2e-25, Strtod(vector, -25));
   CHECK_EQ(2e-39, Strtod(vector, -39));
 
-  OS::StrNCpy(buffer, "9", kBufferSize);
-  vector = Vector<char>(buffer_array, strlen(buffer_array));
+  vector = StringToVector("9");
   CHECK_EQ(9.0, Strtod(vector, 0));
   CHECK_EQ(90.0, Strtod(vector, 1));
   CHECK_EQ(900.0, Strtod(vector, 2));
@@ -86,8 +86,7 @@ TEST(Strtod) {
   CHECK_EQ(9e-25, Strtod(vector, -25));
   CHECK_EQ(9e-39, Strtod(vector, -39));
 
-  OS::StrNCpy(buffer, "12345", kBufferSize);
-  vector = Vector<char>(buffer_array, strlen(buffer_array));
+  vector = StringToVector("12345");
   CHECK_EQ(12345.0, Strtod(vector, 0));
   CHECK_EQ(123450.0, Strtod(vector, 1));
   CHECK_EQ(1234500.0, Strtod(vector, 2));
@@ -109,8 +108,7 @@ TEST(Strtod) {
   CHECK_EQ(12345e-25, Strtod(vector, -25));
   CHECK_EQ(12345e-39, Strtod(vector, -39));
 
-  OS::StrNCpy(buffer, "12345678901234", kBufferSize);
-  vector = Vector<char>(buffer_array, strlen(buffer_array));
+  vector = StringToVector("12345678901234");
   CHECK_EQ(12345678901234.0, Strtod(vector, 0));
   CHECK_EQ(123456789012340.0, Strtod(vector, 1));
   CHECK_EQ(1234567890123400.0, Strtod(vector, 2));
@@ -132,8 +130,7 @@ TEST(Strtod) {
   CHECK_EQ(12345678901234e-25, Strtod(vector, -25));
   CHECK_EQ(12345678901234e-39, Strtod(vector, -39));
 
-  OS::StrNCpy(buffer, "123456789012345", kBufferSize);
-  vector = Vector<char>(buffer_array, strlen(buffer_array));
+  vector = StringToVector("123456789012345");
   CHECK_EQ(123456789012345.0, Strtod(vector, 0));
   CHECK_EQ(1234567890123450.0, Strtod(vector, 1));
   CHECK_EQ(12345678901234500.0, Strtod(vector, 2));
@@ -152,4 +149,53 @@ TEST(Strtod) {
   CHECK_EQ(123456789012345e-23, Strtod(vector, -23));
   CHECK_EQ(123456789012345e-25, Strtod(vector, -25));
   CHECK_EQ(123456789012345e-39, Strtod(vector, -39));
+
+  CHECK_EQ(0.0, StrtodChar("0", 12345));
+  CHECK_EQ(0.0, StrtodChar("", 1324));
+  CHECK_EQ(0.0, StrtodChar("000000000", 123));
+  CHECK_EQ(0.0, StrtodChar("2", -324));
+  CHECK_EQ(3e-324, StrtodChar("3", -324));
+  // It would be more readable to put non-zero literals on the left side (i.e.
+  //   CHECK_EQ(1e-325, StrtodChar("1", -325))), but then Gcc complains that
+  // they are truncated to zero.
+  CHECK_EQ(0.0, StrtodChar("1", -325));
+  CHECK_EQ(0.0, StrtodChar("1", -325));
+  CHECK_EQ(0.0, StrtodChar("20000", -328));
+  CHECK_EQ(30000e-328, StrtodChar("30000", -328));
+  CHECK_EQ(0.0, StrtodChar("10000", -329));
+  CHECK_EQ(0.0, StrtodChar("90000", -329));
+  CHECK_EQ(0.0, StrtodChar("000000001", -325));
+  CHECK_EQ(0.0, StrtodChar("000000001", -325));
+  CHECK_EQ(0.0, StrtodChar("0000000020000", -328));
+  CHECK_EQ(30000e-328, StrtodChar("00000030000", -328));
+  CHECK_EQ(0.0, StrtodChar("0000000010000", -329));
+  CHECK_EQ(0.0, StrtodChar("0000000090000", -329));
+
+  // It would be more readable to put the literals (and not V8_INFINITY) on the
+  // left side (i.e. CHECK_EQ(1e309, StrtodChar("1", 309))), but then Gcc
+  // complains that the floating constant exceeds range of 'double'.
+  CHECK_EQ(V8_INFINITY, StrtodChar("1", 309));
+  CHECK_EQ(1e308, StrtodChar("1", 308));
+  CHECK_EQ(1234e305, StrtodChar("1234", 305));
+  CHECK_EQ(1234e304, StrtodChar("1234", 304));
+  CHECK_EQ(V8_INFINITY, StrtodChar("18", 307));
+  CHECK_EQ(17e307, StrtodChar("17", 307));
+  CHECK_EQ(V8_INFINITY, StrtodChar("0000001", 309));
+  CHECK_EQ(1e308, StrtodChar("00000001", 308));
+  CHECK_EQ(1234e305, StrtodChar("00000001234", 305));
+  CHECK_EQ(1234e304, StrtodChar("000000001234", 304));
+  CHECK_EQ(V8_INFINITY, StrtodChar("0000000018", 307));
+  CHECK_EQ(17e307, StrtodChar("0000000017", 307));
+  CHECK_EQ(V8_INFINITY, StrtodChar("1000000", 303));
+  CHECK_EQ(1e308, StrtodChar("100000", 303));
+  CHECK_EQ(1234e305, StrtodChar("123400000", 300));
+  CHECK_EQ(1234e304, StrtodChar("123400000", 299));
+  CHECK_EQ(V8_INFINITY, StrtodChar("180000000", 300));
+  CHECK_EQ(17e307, StrtodChar("170000000", 300));
+  CHECK_EQ(V8_INFINITY, StrtodChar("00000001000000", 303));
+  CHECK_EQ(1e308, StrtodChar("000000000000100000", 303));
+  CHECK_EQ(1234e305, StrtodChar("00000000123400000", 300));
+  CHECK_EQ(1234e304, StrtodChar("0000000123400000", 299));
+  CHECK_EQ(V8_INFINITY, StrtodChar("00000000180000000", 300));
+  CHECK_EQ(17e307, StrtodChar("00000000170000000", 300));
 }