[libc] Implement strftime

libc/config/gpu/entrypoints.txt

@@ -256,6 +256,8 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.nanosleep
+    libc.src.time.strftime
+    libc.src.time.strftime_l
 
     # wchar.h entrypoints
     libc.src.wchar.wctob

libc/newhdrgen/yaml/time.yaml

@@ -8,6 +8,7 @@ types:
   - type_name: time_t
   - type_name: clock_t
   - type_name: size_t
+  - type_name: locale_t
 enums: []
 objects: []
 functions:
@@ -96,3 +97,22 @@ functions:
     return_type: time_t
     arguments:
       - type: time_t *
+  - name: strftime
+    standard:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: char *__restrict
+      - type: size_t
+      - type: const char *__restrict
+      - type: const struct tm *__restrict
+  - name: strftime_l
+    standard:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: char *__restrict
+      - type: size_t
+      - type: const char *__restrict
+      - type: const struct tm *__restrict
+      - type: locale_t

libc/spec/stdc.td

@@ -1586,6 +1586,7 @@ def StdC : StandardSpec<"stdc"> {
          StructTimeSpec,
          TimeTType,
          SizeTType,
+         LocaleT,
       ],
       [], // Enumerations
       [
@@ -1651,6 +1652,26 @@ def StdC : StandardSpec<"stdc"> {
               RetValSpec<TimeTType>,
               [ArgSpec<TimeTTypePtr>]
           >,
+          FunctionSpec<
+              "strftime",
+              RetValSpec<SizeTType>,
+              [
+                  ArgSpec<CharRestrictedPtr>,
+                  ArgSpec<SizeTType>,
+                  ArgSpec<ConstCharRestrictedPtr>,
+                  ArgSpec<StructTmPtr>
+              ]
+          FunctionSpec<
+              "strftime_l",
+              RetValSpec<SizeTType>,
+              [
+                  ArgSpec<CharRestrictedPtr>,
+                  ArgSpec<SizeTType>,
+                  ArgSpec<ConstCharRestrictedPtr>,
+                  ArgSpec<StructTmPtr>,
+                  ArgSpec<LocaleT>
+              ]
+          >,
       ]
   >;
 

libc/src/time/CMakeLists.txt

@@ -1,6 +1,6 @@
-if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
-  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
-endif()
+# if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+#   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+# endif()
 
 add_object_library(
   time_utils
@@ -99,7 +99,6 @@ add_entrypoint_object(
   HDRS
     mktime.h
   DEPENDS
-    .time_utils
     libc.include.time
     libc.src.errno.errno
 )
@@ -138,3 +137,30 @@ add_entrypoint_object(
   DEPENDS
     .${LIBC_TARGET_OS}.gettimeofday
 )
+
+add_subdirectory(strftime_core)
+
+add_entrypoint_object(
+  strftime
+  SRCS
+    strftime.cpp
+  HDRS
+    strftime.h
+  DEPENDS
+    libc.include.time
+    libc.src.time.strftime_core.strftime_main
+    libc.src.stdio.printf_core.writer
+)
+
+add_entrypoint_object(
+  strftime_l
+  SRCS
+    strftime_l.cpp
+  HDRS
+    strftime_l.h
+  DEPENDS
+    libc.include.time
+    libc.include.locale
+    libc.src.time.strftime_core.strftime_main
+    libc.src.stdio.printf_core.writer
+)

libc/src/time/strftime.cpp

@@ -0,0 +1,31 @@
+//===-- Implementation of strftime function -------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/time/strftime.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/errno/libc_errno.h"
+#include "src/time/time_utils.h"
+
+#include "src/stdio/printf_core/writer.h"
+#include "src/time/strftime_core/strftime_main.h"
+namespace LIBC_NAMESPACE_DECL {
+
+size_t strftime(char *__restrict buffer, size_t buffsz,
+                const char *__restrict format, const struct tm *timeptr) {
+
+  printf_core::WriteBuffer wb(buffer, (buffsz > 0 ? buffsz - 1 : 0),
+                              strftime_core::overflow_write_mock, nullptr);
+  printf_core::Writer writer(&wb);
+  int ret = strftime_core::strftime_main(&writer, format, timeptr);
+  if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
+    wb.buff[wb.buff_cur] = '\0';
+  return ret > 0 ? ret : 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/time/strftime.h

@@ -0,0 +1,23 @@
+//===-- Implementation header of strftime -----------------------*- 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_TIME_STRFTIME_H
+#define LLVM_LIBC_SRC_TIME_STRFTIME_H
+
+#include "src/__support/macros/config.h"
+#include <stddef.h>
+#include <time.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+size_t strftime(char *__restrict, size_t max, const char *__restrict format,
+                const struct tm *timeptr);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_TIME_STRFTIME_H

libc/src/time/strftime_core/CMakeLists.txt

@@ -0,0 +1,57 @@
+add_header_library(
+  core_structs
+  HDRS
+    core_structs.h
+  DEPENDS
+    libc.src.__support.CPP.string_view
+    libc.include.time
+)
+
+add_header_library(
+  parser
+  HDRS
+    parser.h
+  DEPENDS
+    .core_structs
+    libc.src.string.string_utils
+    libc.include.time
+
+)
+
+add_object_library(
+  converter
+  SRCS
+    converter.cpp
+  HDRS
+    converter.h
+    num_converter.h
+    str_converter.h
+    composite_converter.h
+  DEPENDS
+    .core_structs
+    libc.src.__support.arg_list
+    libc.src.stdio.printf_core.writer
+    libc.src.stdio.printf_core.printf_main
+    libc.src.__support.big_int
+    libc.src.__support.CPP.string_view
+    libc.src.__support.float_to_string
+    libc.src.__support.integer_to_string
+    libc.src.__support.uint128
+    libc.src.__support.StringUtil.error_to_string
+    libc.include.time
+
+)
+
+add_object_library(
+  strftime_main
+  SRCS
+    strftime_main.cpp
+  HDRS
+    strftime_main.h
+  DEPENDS
+    .core_structs
+    .parser
+    .converter
+    libc.src.stdio.printf_core.writer
+    libc.include.time
+)

libc/src/time/strftime_core/composite_converter.h

@@ -0,0 +1,124 @@
+//===-- 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_COMPOSITE_CONVERTER_H
+#define LLVM_LIBC_SRC_STDIO_STRFTIME_CORE_COMPOSITE_CONVERTER_H
+
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/arg_list.h"
+#include "src/__support/integer_to_string.h"
+#include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/printf_main.h"
+#include "src/stdio/printf_core/writer.h"
+#include "src/time/strftime_core/core_structs.h"
+#include "src/time/strftime_core/time_internal_def.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace strftime_core {
+
+namespace details {
+int snprintf_impl(char *__restrict buffer, size_t buffsz,
+                  const char *__restrict format, ...) {
+  va_list vlist;
+  va_start(vlist, format);
+  internal::ArgList args(vlist);
+  va_end(vlist);
+  printf_core::WriteBuffer wb(buffer, (buffsz > 0 ? buffsz - 1 : 0));
+  printf_core::Writer writer(&wb);
+
+  int ret_val = printf_core::printf_main(&writer, format, args);
+  if (buffsz > 0)
+    wb.buff[wb.buff_cur] = '\0';
+  return ret_val;
+}
+} // namespace details
+
+int write_composite(printf_core::Writer *writer, const FormatSection &to_conv) {
+  char buffer[100];
+  auto &time = *to_conv.time;
+
+  switch (to_conv.conv_name) {
+  // Full date and time representation (e.g., equivalent to %a %b %e %T %Y)
+  case 'c': {
+    RET_IF_RESULT_NEGATIVE(details::snprintf_impl(
+        buffer, sizeof(buffer), "%s %s %02d %02d:%02d:%02d %d",
+        safe_abbreviated_day_name(time.tm_wday),
+        safe_abbreviated_month_name(time.tm_mon), time.tm_mday, time.tm_hour,
+        time.tm_min, time.tm_sec, time.tm_year + 1900));
+    break;
+  }
+
+  // Zero-padded day of the month (equivalent to %m/%d/%y)
+  case 'D': {
+    RET_IF_RESULT_NEGATIVE(details::snprintf_impl(
+        buffer, sizeof(buffer), "%02d/%02d/%02d", time.tm_mon + 1, time.tm_mday,
+        (time.tm_year + 1900) % 100));
+    break;
+  }
+
+  // ISO 8601 date representation in YYYY-MM-DD (equivalent to %Y-%m-%d)
+  case 'F': {
+    RET_IF_RESULT_NEGATIVE(details::snprintf_impl(
+        buffer, sizeof(buffer), "%04d-%02d-%02d", time.tm_year + 1900,
+        time.tm_mon + 1, time.tm_mday));
+    break;
+  }
+
+  // 12-hour clock time with seconds and AM/PM (equivalent to %I:%M:%S %p)
+  case 'r': {
+    int hour12 = time.tm_hour % 12;
+    if (hour12 == 0)
+      hour12 = 12;
+    RET_IF_RESULT_NEGATIVE(details::snprintf_impl(
+        buffer, sizeof(buffer), "%02d:%02d:%02d %s", hour12, time.tm_min,
+        time.tm_sec,
+        to_conv.time->tm_hour >= 12 ? default_PM_str : default_AM_str));
+    break;
+  }
+
+  // 24-hour time without seconds (equivalent to %H:%M)
+  case 'R': {
+    RET_IF_RESULT_NEGATIVE(details::snprintf_impl(
+        buffer, sizeof(buffer), "%02d:%02d", time.tm_hour, time.tm_min));
+    break;
+  }
+
+  // Time with seconds (equivalent to %H:%M:%S)
+  case 'T': {
+    RET_IF_RESULT_NEGATIVE(
+        details::snprintf_impl(buffer, sizeof(buffer), "%02d:%02d:%02d",
+                               time.tm_hour, time.tm_min, time.tm_sec));
+    break;
+  }
+
+  // Locale's date representation (often equivalent to %m/%d/%y)
+  case 'x': {
+    RET_IF_RESULT_NEGATIVE(details::snprintf_impl(
+        buffer, sizeof(buffer), "%02d/%02d/%02d", time.tm_mon + 1, time.tm_mday,
+        (time.tm_year + 1900) % 100));
+    break;
+  }
+
+  // Locale's time representation (equivalent to %H:%M:%S)
+  case 'X': {
+    RET_IF_RESULT_NEGATIVE(
+        details::snprintf_impl(buffer, sizeof(buffer), "%02d:%02d:%02d",
+                               time.tm_hour, time.tm_min, time.tm_sec));
+    break;
+  }
+
+  default:
+    return writer->write(to_conv.raw_string);
+  }
+  return writer->write(buffer);
+}
+
+} // namespace strftime_core
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif