[libc-commits] [libc] [libc] implement pathconf/fpathconf (PR #87165)

[Schrodinger ZHU Yifan via libc-commits]

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@@ -0,0 +1,121 @@
+//===-- Linux implementation of pathconf ----------------------------------===//
+//
+// 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/unistd/pread.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/__support/macros/sanitizer.h" // for MSAN_UNPOISON
+#include "src/errno/libc_errno.h"
+#include <stdint.h> // For uint64_t.
+#include <sys/fstatvfs.h>
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE {
+
+static long filesizebits(const struct statfs &s) {
+  switch (s.f_type) {
+  case JFFS2_SUPER_MAGIC:
+  case MSDOS_SUPER_MAGIC:
+  case NCP_SUPER_MAGIC:
+    return 32;
+  }
+  return 64;
+}
+
+static long link_max(const struct statfs &s) {
+  switch (s.f_type) {
+  case EXT2_SUPER_MAGIC:
+    return 32000;
+  case MINIX_SUPER_MAGIC:
+    return 250;
+  case MINIX2_SUPER_MAGIC:
+    return 65530;
+  case REISERFS_SUPER_MAGIC:
+    return 0xffff - 1000;
+  case UFS_MAGIC:
+    return 32000;
+  }
+  return LINK_MAX;
+}
+
+static long _2_symlinks(const struct statfs &s) {
+  switch (s.f_type) {
+  case ADFS_SUPER_MAGIC:
+  case BFS_MAGIC:
+  case CRAMFS_MAGIC:
+  case EFS_SUPER_MAGIC:
+  case MSDOS_SUPER_MAGIC:
+  case QNX4_SUPER_MAGIC:
+    return 0;
+  }
+  return 1;
+}
+
+static long pathconfig(const struct statfs &s, int name) {
+  switch (name) {
+  case _PC_LINK_MAX:
+    return link_max(s);
+
+  case _PC_FILESIZEBITS:
+    return filesizebits(s);
+
+  case _PC_2_SYMLINKS:
+    return _2_symlinks(s);
+
+  case _PC_REC_MIN_XFER_SIZE:
+    return s.f_bsize;
+
+  case _PC_ALLOC_SIZE_MIN:
+  case _PC_REC_XFER_ALIGN:
+    return s.f_frsize;
+
+  case _PC_MAX_CANON:
+    return _POSIX_MAX_CANON;
+
+  case _PC_MAX_INPUT:
+    return _POSIX_MAX_INPUT;
+
+  case _PC_NAME_MAX:
+    return s.f_namemax;
+
+  case _PC_PATH_MAX:
+    return _POSIX_PATH_MAX;
+
+  case _PC_PIPE_BUF:
+    return _POSIX_PIPE_BUF;
+
+  case _PC_CHOWN_RESTRICTED:
+    return _POSIX_CHOWN_RESTRICTED;
+
+  case _PC_NO_TRUNC:
+    return _POSIX_NO_TRUNC;
+
+  case _PC_VDISABLE:
+    return _POSIX_VDISABLE;
+
+  case _PC_ASYNC_IO:
+  case _PC_PRIO_IO:
+  case _PC_REC_INCR_XFER_SIZE:
+  case _PC_REC_MAX_XFER_SIZE:
+  case _PC_SYMLINK_MAX:
+  case _PC_SYNC_IO:
+  default:
+    return -1;
+  }
+}
+
+LLVM_LIBC_FUNCTION(long, pathconf, (char *path, int name)) {
+  cpp::optional<LinuxStatFs> result = linux_statfs(const char *path);
+  if (!result.has_value()) {
+    return -1;
+  }
+  return pathconfig(result.value(), name);
----------------
SchrodingerZhu wrote:

> If the implementation needs to use fildes to determine the value of name and the implementation does not support the association of name with the file specified by fildes, or if fildes is an invalid file descriptor, fpathconf() shall return -1 and set errno to indicate the error.

Should we update `errno`?

https://github.com/llvm/llvm-project/pull/87165