[libc] Implement strftime

Author: tszhin-swe

libc/src/stdio/CMakeLists.txt

@@ -239,6 +239,7 @@ add_entrypoint_object(
 
 add_subdirectory(printf_core)
 add_subdirectory(scanf_core)
+add_subdirectory(strftime_core)
 
 add_entrypoint_object(
   remove

libc/src/stdio/strftime_core/CMakeLists.txt

@@ -0,0 +1,52 @@
+
+add_header_library(
+  core_structs
+  HDRS
+    core_structs.h
+  DEPENDS
+    libc.src.__support.CPP.string_view
+    libc.src.__support.FPUtil.fp_bits
+)
+
+add_header_library(
+  parser
+  HDRS
+    parser.h
+  DEPENDS
+    .core_structs
+    libc.src.__support.arg_list
+    libc.src.__support.ctype_utils
+    libc.src.__support.str_to_integer
+    libc.src.__support.CPP.algorithm
+    libc.src.__support.CPP.bit
+    libc.src.__support.CPP.optional
+    libc.src.__support.CPP.string_view
+    libc.src.__support.CPP.type_traits
+    libc.src.__support.common
+)
+
+
+add_object_library(
+  converter
+  SRCS
+    converter.cpp
+  HDRS
+    converter.h
+  DEPENDS
+    .core_structs
+    libc.src.stdio.printf_core.writer
+    libc.src.__support.big_int
+    libc.src.math.log10
+    libc.src.__support.common
+    libc.src.__support.CPP.limits
+    libc.src.__support.CPP.span
+    libc.src.__support.CPP.string_view
+    libc.src.__support.float_to_string
+    libc.src.__support.FPUtil.fenv_impl
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.rounding_mode
+    libc.src.__support.integer_to_string
+    libc.src.__support.libc_assert
+    libc.src.__support.uint128
+    libc.src.__support.StringUtil.error_to_string
+)

libc/src/stdio/strftime_core/converter.cpp

@@ -0,0 +1,264 @@
+//===-- Format specifier converter for printf -------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See htto_conv.times://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDIO_STRFTIME_CORE_CONVERTER_H
+#define LLVM_LIBC_SRC_STDIO_STRFTIME_CORE_CONVERTER_H
+
+#include "src/__support/CPP/string.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/integer_to_string.h"
+#include "src/__support/macros/config.h"
+#include "src/math/log10.h"
+#include "src/stdio/printf_core/writer.h"
+#include "src/stdio/strftime_core/core_structs.h"
+#include "src/stdio/strftime_core/time_internal_def.h"
+#include <time.h>
+
+namespace LIBC_NAMESPACE_DECL {
+namespace strftime_core {
+
+namespace details {
+
+LIBC_INLINE cpp::optional<cpp::string_view>
+num_to_strview(uintmax_t num, cpp::span<char> bufref) {
+  return IntegerToString<uintmax_t>::format_to(bufref, num);
+}
+
+template <int width>
+LIBC_INLINE int write_num(uintmax_t num, printf_core::Writer *writer) {
+  cpp::array<char, width> buf;
+  return writer->write(*num_to_strview(num, buf));
+}
+
+template <int width, char padding>
+LIBC_INLINE int write_num_with_padding(uintmax_t num,
+                                       printf_core::Writer *writer) {
+  cpp::array<char, width> buf;
+  auto digits = log10(num) + 1;
+  auto padding_needed = width - digits;
+  int char_written = 0;
+  for (int _ = 0; _ < padding_needed; _++) {
+    char_written += writer->write(padding);
+  }
+  char_written += writer->write(*num_to_strview(num, buf));
+  return char_written;
+}
+
+} // namespace details
+
+/* Nonzero if YEAR is a leap year (every 4 years,
+   except every 100th isn't, and every 400th is).  */
+LIBC_INLINE bool is_leap(int year) {
+  return ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0));
+}
+
+LIBC_INLINE int convert_weekday(printf_core::Writer *writer,
+                                const FormatSection &to_conv) {
+  return writer->write(day_names[to_conv.time->tm_wday]);
+}
+
+LIBC_INLINE int convert_zero_padded_day_of_year(printf_core::Writer *writer,
+                                                const FormatSection &to_conv) {
+  return details::write_num_with_padding<3, '0'>(to_conv.time->tm_yday + 1,
+                                                 writer);
+}
+
+LIBC_INLINE int convert_zero_padded_day_of_month(printf_core::Writer *writer,
+                                                 const FormatSection &to_conv) {
+  return details::write_num_with_padding<2, '0'>(to_conv.time->tm_mday, writer);
+}
+
+LIBC_INLINE int
+convert_space_padded_day_of_month(printf_core::Writer *writer,
+                                  const FormatSection &to_conv) {
+  return details::write_num_with_padding<2, ' '>(to_conv.time->tm_mday, writer);
+}
+
+LIBC_INLINE int convert_decimal_weekday(printf_core::Writer *writer,
+                                        const FormatSection &to_conv) {
+  return details::write_num<1>(
+      to_conv.time->tm_wday == 0 ? 7 : to_conv.time->tm_wday, writer);
+}
+
+LIBC_INLINE int convert_decimal_weekday_iso(printf_core::Writer *writer,
+                                            const FormatSection &to_conv) {
+  return details::write_num<1>(to_conv.time->tm_wday, writer);
+}
+
+LIBC_INLINE int convert_week_number_sunday(printf_core::Writer *writer,
+                                           const FormatSection &to_conv) {
+  int wday = to_conv.time->tm_wday;
+  int yday = to_conv.time->tm_yday;
+  int week = (yday - wday + 7) / 7;
+  return details::write_num_with_padding<2, '0'>(week, writer);
+}
+
+LIBC_INLINE int convert_week_number_monday(printf_core::Writer *writer,
+                                           const FormatSection &to_conv) {
+  int wday = (to_conv.time->tm_wday + 6) % 7;
+  int yday = to_conv.time->tm_yday;
+  int week = (yday - wday + 7) / 7;
+  return details::write_num_with_padding<2, '0'>(week, writer);
+}
+
+LIBC_INLINE int convert_full_month(printf_core::Writer *writer,
+                                   const FormatSection &to_conv) {
+  return writer->write(month_names[to_conv.time->tm_mon]);
+}
+
+LIBC_INLINE int convert_abbreviated_month(printf_core::Writer *writer,
+                                          const FormatSection &to_conv) {
+  return writer->write(abbreviated_month_names[to_conv.time->tm_mon]);
+}
+
+LIBC_INLINE int convert_zero_padded_month(printf_core::Writer *writer,
+                                          const FormatSection &to_conv) {
+  return details::write_num_with_padding<2, '0'>(to_conv.time->tm_mon + 1,
+                                                 writer);
+}
+
+LIBC_INLINE int convert_full_year(printf_core::Writer *writer,
+                                  const FormatSection &to_conv) {
+  return details::write_num_with_padding<4, '0'>(
+      to_conv.time->tm_year + YEAR_BASE, writer);
+}
+
+LIBC_INLINE int convert_two_digit_year(printf_core::Writer *writer,
+                                       const FormatSection &to_conv) {
+  return details::write_num_with_padding<2, '0'>(
+      (to_conv.time->tm_year + YEAR_BASE) % 100, writer);
+}
+
+LIBC_INLINE int convert_century(printf_core::Writer *writer,
+                                const FormatSection &to_conv) {
+  return details::write_num_with_padding<2, '0'>(
+      (to_conv.time->tm_year + YEAR_BASE) / 100, writer);
+}
+
+static int iso_week_days(int yday, int wday) {
+  /* Add enough to the first operand of % to make it nonnegative.  */
+  int big_enough_multiple_of_7 = (-YDAY_MINIMUM / 7 + 2) * 7;
+  return (yday - (yday - wday + ISO_WEEK1_WDAY + big_enough_multiple_of_7) % 7 +
+          ISO_WEEK1_WDAY - ISO_WEEK_START_WDAY);
+}
+
+LIBC_INLINE int convert_iso_year(printf_core::Writer *writer,
+                                 const FormatSection &to_conv) {
+  int year = to_conv.time->tm_year + YEAR_BASE;
+  int days = iso_week_days(to_conv.time->tm_yday, to_conv.time->tm_wday);
+
+  if (days < 0) {
+    /* This ISO week belongs to the previous year.  */
+    year--;
+    days = iso_week_days(to_conv.time->tm_yday + (365 + is_leap(year)),
+                         to_conv.time->tm_wday);
+  } else {
+    int d = iso_week_days(to_conv.time->tm_yday - (365 + is_leap(year)),
+                          to_conv.time->tm_wday);
+    if (0 <= d) {
+      /* This ISO week belongs to the next year.  */
+      year++;
+      days = d;
+    }
+  }
+
+  return details::write_num<4>(year, writer);
+}
+
+LIBC_INLINE int convert_hour_24(printf_core::Writer *writer,
+                                const FormatSection &to_conv) {
+  return details::write_num_with_padding<2, '0'>(to_conv.time->tm_hour, writer);
+}
+
+LIBC_INLINE int convert_pm(printf_core::Writer *writer,
+                           const FormatSection &to_conv) {
+  static const cpp::string_view AM = "AM";
+  static const cpp::string_view PM = "PM";
+  return writer->write(to_conv.time->tm_hour >= 12 ? PM : AM);
+}
+
+LIBC_INLINE int convert_hour_12(printf_core::Writer *writer,
+                                const FormatSection &to_conv) {
+  int hour = to_conv.time->tm_hour % 12; // Convert to 12-hour format
+  if (hour == 0)
+    hour = 12; // Adjust for midnight
+  return details::write_num_with_padding<2, '0'>(hour, writer);
+}
+
+LIBC_INLINE int convert_minute(printf_core::Writer *writer,
+                               const FormatSection &to_conv) {
+  return details::write_num_with_padding<2, '0'>(to_conv.time->tm_min, writer);
+}
+
+LIBC_INLINE int convert_second(printf_core::Writer *writer,
+                               const FormatSection &to_conv) {
+  return details::write_num_with_padding<2, '0'>(to_conv.time->tm_sec, writer);
+}
+
+int convert(printf_core::Writer *writer, const FormatSection &to_conv) {
+  if (!to_conv.has_conv)
+    return writer->write(to_conv.raw_string);
+  switch (to_conv.conv_name) {
+  // day of the week
+  case 'a':
+    return convert_weekday(writer, to_conv);
+  case 'w':
+    return convert_decimal_weekday(writer, to_conv);
+  case 'u':
+    return convert_decimal_weekday_iso(writer, to_conv);
+  // day of the year/ month
+  case 'j':
+    return convert_zero_padded_day_of_year(writer, to_conv);
+  case 'd':
+    return convert_zero_padded_day_of_month(writer, to_conv);
+  case 'e':
+    return convert_space_padded_day_of_month(writer, to_conv);
+  // week
+  case 'U':
+    return convert_week_number_sunday(writer, to_conv);
+  case 'W':
+    return convert_week_number_monday(writer, to_conv);
+  case 'V': // TODO: ISO 8061
+  // month
+  case 'B':
+    return convert_full_month(writer, to_conv);
+  case 'b':
+  case 'h':
+    return convert_abbreviated_month(writer, to_conv);
+  case 'm':
+    return convert_zero_padded_month(writer, to_conv);
+  // year
+  case 'Y':
+    return convert_full_year(writer, to_conv);
+  case 'y':
+    return convert_two_digit_year(writer, to_conv);
+  case 'C':
+    return convert_century(writer, to_conv);
+  case 'G':
+    // TODO
+    return convert_iso_year(writer, to_conv);
+  // hours
+  case 'p':
+    return convert_pm(writer, to_conv);
+  case 'H':
+    return convert_hour_24(writer, to_conv);
+  case 'I':
+    return convert_hour_12(writer, to_conv);
+  // minutes
+  case 'M':
+    return convert_minute(writer, to_conv);
+  // seconds
+  case 'S':
+    return convert_second(writer, to_conv);
+  }
+  return 0;
+}
+
+} // namespace strftime_core
+} // namespace LIBC_NAMESPACE_DECL
+#endif

libc/src/stdio/strftime_core/converter.h

@@ -0,0 +1,29 @@
+//===-- Format specifier converter for printf -------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDIO_STRFTIME_CORE_CONVERTER_H
+#define LLVM_LIBC_SRC_STDIO_STRFTIME_CORE_CONVERTER_H
+
+#include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/writer.h"
+#include "src/stdio/strftime_core/core_structs.h"
+
+#include <stddef.h>
+
+namespace LIBC_NAMESPACE_DECL {
+namespace strftime_core {
+
+// convert will call a conversion function to convert the FormatSection into
+// its string representation, and then that will write the result to the
+// writer.
+int convert(printf_core::Writer *writer, const FormatSection &to_conv);
+
+} // namespace strftime_core
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDIO_STRFTIME_CORE_CONVERTER_H