Revert "Implement some formatting options in Grisu"

This reverts commit 2a952dd0b2.

include/fmt/format-inl.h

@@ -364,14 +364,12 @@ FMT_FUNC fp get_cached_power(int min_exponent, int &pow10_exponent) {
   return fp(data::POW10_SIGNIFICANDS[index], data::POW10_EXPONENTS[index]);
 }
 
-// Writes the exponent exp in the form "[+-]d{1,3}" to buffer.
+// Writes the exponent exp in the form "[-]d{1,3}" to buffer.
 FMT_FUNC char *write_exponent(char *buffer, int exp) {
   FMT_ASSERT(-1000 < exp && exp < 1000, "exponent out of range");
   if (exp < 0) {
     *buffer++ = '-';
     exp = -exp;
-  } else {
-    *buffer++ = '+';
   }
   if (exp >= 100) {
     *buffer++ = '0' + static_cast<char>(exp / 100);
@@ -448,40 +446,9 @@ FMT_FUNC void grisu2_gen_digits(
 
 // Prettifies the output of the Grisu2 algorithm.
 // The number is given as v = buffer * 10^exp.
-FMT_FUNC void grisu2_prettify(char *buffer, size_t &size, int exp, char type,
-                              int precision, bool print_decimal_point) {
-  int int_size = static_cast<int>(size);
+FMT_FUNC void grisu2_prettify(char *buffer, size_t &size, int exp) {
   // 10^(full_exp - 1) <= v <= 10^full_exp.
-  int full_exp = int_size + exp;
-  if (int_size <= full_exp && full_exp <= 21) {
-    // 1234e7 -> 12340000000
-    char *p = std::uninitialized_fill_n(
-          buffer + int_size, full_exp - int_size, '0');
-    if (print_decimal_point && int_size < precision) {
-      *p++ = '.';
-      p = std::uninitialized_fill_n(p, precision - int_size, '0');
-    }
-    size = to_unsigned(p - buffer);
-  } else if (0 < full_exp && full_exp <= 21) {
-    // 1234e-2 -> 12.34
-    size_t fractional_size = int_size - full_exp;
-    std::memmove(buffer + full_exp + 1, buffer + full_exp, fractional_size);
-    buffer[full_exp] = '.';
-    if (type == 'f' && fractional_size < precision) {
-      size_t num_zeros = precision - fractional_size;
-      std::uninitialized_fill_n(buffer + size + 1, num_zeros, '0');
-      size += num_zeros;
-    }
-    ++size;
-  } else if (-6 < full_exp && full_exp <= 0) {
-    // 1234e-6 -> 0.001234
-    int offset = 2 - full_exp;
-    std::memmove(buffer + offset, buffer, size);
-    buffer[0] = '0';
-    buffer[1] = '.';
-    std::uninitialized_fill_n(buffer + 2, -full_exp, '0');
-    size = to_unsigned(int_size + offset);
-  } else {
+  int full_exp = static_cast<int>(size) + exp;
   // Insert a decimal point after the first digit and add an exponent.
   std::memmove(buffer + 2, buffer + 1, size - 1);
   buffer[1] = '.';
@@ -489,15 +456,15 @@ FMT_FUNC void grisu2_prettify(char *buffer, size_t &size, int exp, char type,
   *p++ = 'e';
   size = to_unsigned(write_exponent(p, full_exp - 1) - buffer);
 }
-}
 
-FMT_FUNC void grisu2_format_positive(double value, char *buffer, size_t &size,
-                                     int &dec_exp) {
-  FMT_ASSERT(value > 0, "value is nonpositive");
+// Formats value using Grisu2 algorithm. Grisu2 doesn't give any guarantees on
+// the shortness of the result.
+FMT_FUNC void grisu2_format(double value, char *buffer, size_t &size) {
   fp fp_value(value);
   fp lower, upper;  // w^- and w^+ in the Grisu paper.
   fp_value.compute_boundaries(lower, upper);
   // Find a cached power of 10 close to 1 / upper.
+  int dec_exp = 0;  // K in Grisu.
   const int min_exp = -60;  // alpha in Grisu.
   auto dec_pow = get_cached_power(  // \tilde{c}_{-k} in Grisu.
       min_exp - (upper.e + fp::significand_size), dec_exp);
@@ -510,27 +477,7 @@ FMT_FUNC void grisu2_format_positive(double value, char *buffer, size_t &size,
   --scaled_upper.f;  // \tilde{M}^+ - 1 ulp -> M^+_{\downarrow}.
   uint64_t delta = scaled_upper.f - scaled_lower.f;
   grisu2_gen_digits(scaled_value, scaled_upper, delta, buffer, size, dec_exp);
-}
-
-// Formats value using Grisu2 algorithm. Grisu2 doesn't give any guarantees on
-// the shortness of the result.
-FMT_FUNC void grisu2_format(double value, char *buffer, size_t &size, char type,
-                            int precision, bool print_decimal_point) {
-  int dec_exp = 0;  // K in Grisu.
-  if (value != 0) {
-    grisu2_format_positive(value, buffer, size, dec_exp);
-  } else {
-    *buffer = '0';
-    size = 1;
-  }
-  if (precision < 0)
-    precision = 6;
-  if (size > precision) {
-    // TODO: round instead of truncating
-    dec_exp += size - precision;
-    size = precision;
-  }
-  grisu2_prettify(buffer, size, dec_exp, type, precision, print_decimal_point);
+  grisu2_prettify(buffer, size, dec_exp);
 }
 }  // namespace internal
 

include/fmt/format.h

@@ -367,8 +367,7 @@ FMT_API fp get_cached_power(int min_exponent, int &pow10_exponent);
 
 // Formats value using Grisu2 algorithm:
 // https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf
-FMT_API void grisu2_format(double value, char *buffer, size_t &size, char type,
-                           int precision, bool print_decimal_point);
+FMT_API void grisu2_format(double value, char *buffer, size_t &size);
 
 template <typename Allocator>
 typename Allocator::value_type *allocate(Allocator& alloc, std::size_t n) {
@@ -2950,12 +2949,12 @@ void basic_writer<Range>::write_double(T value, const format_specs &spec) {
   basic_memory_buffer<char_type> buffer;
   if (internal::const_check(FMT_USE_GRISU && sizeof(T) <= sizeof(double) &&
       std::numeric_limits<double>::is_iec559)) {
-    char buf[100]; // TODO: correct buffer size
+    // The max size = 10 (hi) + 20 (lo) + 5 (exp).
+    enum { BUF_SIZE = 35 };
+    char buf[BUF_SIZE];
     size_t size = 0;
-    internal::grisu2_format(
-          static_cast<double>(value), buf, size, static_cast<char>(spec.type()),
-          spec.precision(), spec.flag(HASH_FLAG));
-    FMT_ASSERT(size <= 100, "buffer overflow");
+    internal::grisu2_format(static_cast<double>(value), buf, size);
+    FMT_ASSERT(size <= BUF_SIZE, "buffer overflow");
     buffer.append(buf, buf + size); // TODO: avoid extra copy
   } else {
     format_specs normalized_spec(spec);