[libc-commits] [libc] [libc] Implement strftime (PR #122556)

[Michael Jones via libc-commits]

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@@ -0,0 +1,78 @@
+//===-- String converter for strftime ---------------------------*- 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_STR_CONVERTER_H
+#define LLVM_LIBC_SRC_STDIO_STRFTIME_CORE_STR_CONVERTER_H
+
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/writer.h"
+#include "src/time/strftime_core/core_structs.h"
+#include "src/time/time_constants.h"
+#include "src/time/time_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace strftime_core {
+
+static constexpr cpp::string_view OUT_OF_BOUNDS_STR = "?";
+
+LIBC_INLINE cpp::string_view
+unwrap_opt(cpp::optional<cpp::string_view> str_opt) {
+  if (str_opt.has_value())
+    return *str_opt;
+  else
+    return OUT_OF_BOUNDS_STR;
+}
+
+LIBC_INLINE int convert_str(printf_core::Writer *writer,
+                            const FormatSection &to_conv, const tm *timeptr) {
+  cpp::string_view str;
+  cpp::optional<cpp::string_view> str_opt;
+  const time_utils::TMReader time_reader(timeptr);
+
+  switch (to_conv.conv_name) {
+  case 'a': // Abbreviated weekday name
+    str_opt = time_reader.get_weekday_short_name();
+    str = unwrap_opt(str_opt);
+    break;
+  case 'A': // Full weekday name
+    str_opt = time_reader.get_weekday_full_name();
+    str = unwrap_opt(str_opt);
+    break;
+  case 'b': // Abbreviated month name
+  case 'h': // same as 'b'
+    str_opt = time_reader.get_month_short_name();
+    str = unwrap_opt(str_opt);
+    break;
+  case 'B': // Full month name
+    str_opt = time_reader.get_month_full_name();
+    str = unwrap_opt(str_opt);
+    break;
+  case 'p': // AM/PM designation
+    str = time_reader.get_am_pm();
+    break;
+  case 'Z': // Timezone name
+    // the standard says if no time zone is determinable, write no characters.
+    return WRITE_OK;
+    // str = time_reader.get_timezone_name();
+    break;
+  default:
+    __builtin_trap(); // this should be unreachable, but trap if you hit it.
+  }
+
+  int spaces = to_conv.min_width - static_cast<int>(str.size());
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michaelrj-google wrote:

no, it's a valid string with a size.

https://github.com/llvm/llvm-project/pull/122556