[libc] Add implementation of POSIX lseek function.

[lntue]

libc/include/llvm-libc-macros/file-seek-macros.h

8–9

I think you should change the header guard to match the file name.

libc/test/src/unistd/lseek_test.cpp

2

*lseek

[sivachandra]

Fix up doc comments and header guards.

libc/config/linux/aarch64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
 
     # sys/stat.h entrypoints
     libc.src.sys.stat.mkdir
     libc.src.sys.stat.mkdirat
 
     # unistd.h entrypoints
     libc.src.unistd.close
     libc.src.unistd.fsync
+    libc.src.unistd.lseek
     libc.src.unistd.read
     libc.src.unistd.rmdir
     libc.src.unistd.unlink
     libc.src.unistd.unlinkat
     libc.src.unistd.write
 )
 
 set(TARGET_LIBM_ENTRYPOINTS

libc/config/linux/api.td

let Enumerations = [
     "thrd_success",
     "thrd_busy",
     "thrd_error",
     "thrd_nomem",
   ];
 }
 
 def UniStdAPI : PublicAPI<"unistd.h"> {
-  let Types = ["size_t", "ssize_t"];
+  let Types = ["off_t", "size_t", "ssize_t"];
 }
 
 def SysStatAPI : PublicAPI<"sys/stat.h"> {
   let Types = ["mode_t"];
 }

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
 
     # sys/stat.h entrypoints
     libc.src.sys.stat.mkdir
     libc.src.sys.stat.mkdirat
 
     # unistd.h entrypoints
     libc.src.unistd.close
     libc.src.unistd.fsync
+    libc.src.unistd.lseek
     libc.src.unistd.read
     libc.src.unistd.rmdir
     libc.src.unistd.unlink
     libc.src.unistd.unlinkat
     libc.src.unistd.write
 )
 
 set(TARGET_LIBM_ENTRYPOINTS

libc/include/CMakeLists.txt

 )
 
 add_gen_header(
   stdio
   DEF_FILE stdio.h.def
   GEN_HDR stdio.h
   DEPENDS
     .llvm_libc_common_h
-    .llvm-libc-macros.stdio_macros
+    .llvm-libc-macros.file_seek_macros
     .llvm-libc-types.FILE
     .llvm-libc-types.size_t
 )
 
 add_gen_header(
   stdlib
   DEF_FILE stdlib.h.def
   GEN_HDR stdlib.h

 )
 
 add_gen_header(
   unistd
   DEF_FILE unistd.h.def
   GEN_HDR unistd.h
   DEPENDS
     .llvm_libc_common_h
+    .llvm-libc-macros.file_seek_macros
     .llvm-libc-types.size_t
     .llvm-libc-types.ssize_t
 )
 
 # TODO: Not all platforms will have a include/sys directory. Add the sys
 # directory and the targets for sys/*.h files conditional to the OS requiring
 # them.
 file(MAKE_DIRECTORY "sys")

libc/include/llvm-libc-macros/CMakeLists.txt

 add_subdirectory(linux)
 
 add_header(
   fcntl_macros
   HDR
     fcntl-macros.h
   DEPENDS
     .linux.fcntl_macros
 )
 
 add_header(
-  stdio_macros
+  file_seek_macros
   HDR
-    stdio-macros.h
+    file-seek-macros.h
 )

libc/include/llvm-libc-macros/file-seek-macros.h

-//===-- Definition of macros from stdio.h ---------------------------------===//
+//===-- Definition of macros to be used with file seek functions ----------===//
 //
 // 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_MACROS_STDIO_MACROS_H
-#define __LLVM_LIBC_MACROS_STDIO_MACROS_H
+#ifndef __LLVM_LIBC_MACROS_FILE_SEEK_MACROS_H
+#define __LLVM_LIBC_MACROS_FILE_SEEK_MACROS_H
 
 #define SEEK_SET 0
 #define SEEK_CUR 1
 #define SEEK_END 2
 
-#endif // __LLVM_LIBC_MACROS_STDIO_MACROS_H
+#endif // __LLVM_LIBC_MACROS_FILE_SEEK_MACROS_H

libc/include/stdio.h.def

 //===-- C standard library header stdio.h ---------------------------------===//
 //
 // 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_STDIO_H
 #define LLVM_LIBC_STDIO_H
 
 #include <__llvm-libc-common.h>
-#include <llvm-libc-macros/stdio-macros.h>
+#include <llvm-libc-macros/file-seek-macros.h>
 
 %%public_api()
 
 #endif // LLVM_LIBC_STDIO_H

libc/include/unistd.h.def

 //===-- C standard library header unistd.h --------------------------------===//
 //
 // 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_UNISTD_H
 #define LLVM_LIBC_UNISTD_H
 
 #include <__llvm-libc-common.h>
+#include <llvm-libc-macros/file-seek-macros.h>
 
 %%public_api()
 
 #endif // LLVM_LIBC_UNISTD_H

libc/spec/posix.td

HeaderSpec Signal = HeaderSpec<
         >,
       ]
   >;
 
   HeaderSpec UniStd = HeaderSpec<
     "unistd.h",
     [], // Macros
     [
+      OffTType,
       SSizeTType,
       SizeTType,
     ],
     [], // Enumerations
     [
         FunctionSpec<
           "close",
           RetValSpec<IntType>,
           [ArgSpec<IntType>]
         >,
         FunctionSpec<
           "fsync",
           RetValSpec<IntType>,
           [ArgSpec<IntType>]
         >,
         FunctionSpec<
+          "lseek",
+          RetValSpec<OffTType>,
+          [ArgSpec<IntType>, ArgSpec<OffTType>, ArgSpec<IntType>]
+        >,
+        FunctionSpec<
           "read",
           RetValSpec<SSizeTType>,
           [ArgSpec<IntType>, ArgSpec<VoidPtr>, ArgSpec<SizeTType>]
         >,
         FunctionSpec<
           "rmdir",
           RetValSpec<IntType>,
           [ArgSpec<ConstCharPtr>]

libc/src/unistd/CMakeLists.txt

 add_entrypoint_object(
   fsync
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.fsync
 )
 
 add_entrypoint_object(
+  lseek
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.lseek
+)
+
+add_entrypoint_object(
   read
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.read
 )
 
 add_entrypoint_object(
   rmdir

libc/src/unistd/linux/CMakeLists.txt

add_entrypoint_object(
   DEPENDS
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
 )
 
 add_entrypoint_object(
+  lseek
+  SRCS
+    lseek.cpp
+  HDRS
+    ../lseek.h
+  DEPENDS
+    libc.include.unistd
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
   read
   SRCS
     read.cpp
   HDRS
     ../read.h
   DEPENDS
     libc.include.unistd
     libc.include.sys_syscall

libc/src/unistd/linux/lseek.cpp

+//===-- Linux implementation of lseek -------------------------------------===//
+//
+// 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/lseek.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers.
+#include <unistd.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(off_t, lseek, (int fd, off_t offset, int whence)) {
+  off_t result;
+#ifdef SYS_lseek
+  long ret = __llvm_libc::syscall(SYS_lseek, fd, offset, whence);
+  result = ret;
+#elif defined(SYS__llseek)
+  long ret = __llvm_libc::syscall(SYS__lseek, fd, offset >> 32, offset, &result,
+                                  whence);
+#else
+#error "lseek and _llseek syscalls not available."
+#endif
+
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return result;
+}
+
+} // namespace __llvm_libc

libc/src/unistd/lseek.h

+//===-- Implementation header for lseek -------------------------*- 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_UNISTD_LSEEK_H
+#define LLVM_LIBC_SRC_UNISTD_LSEEK_H
+
+#include <unistd.h>
+
+namespace __llvm_libc {
+
+off_t lseek(int fd, off_t offset, int whence);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_LSEEK_H

libc/test/src/unistd/CMakeLists.txt

DEPENDS
     libc.src.unistd.close
     libc.src.unistd.fsync
     libc.src.unistd.read
     libc.src.unistd.write
     libc.test.errno_setter_matcher
 )
 
 add_libc_unittest(
+  lseek_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    lseek_test.cpp
+  DEPENDS
+    libc.include.errno
+    libc.include.unistd
+    libc.src.fcntl.open
+    libc.src.unistd.close
+    libc.src.unistd.lseek
+    libc.src.unistd.read
+    libc.test.errno_setter_matcher
+)
+
+add_libc_unittest(
   rmdir_test
   SUITE
     libc_unistd_unittests
   SRCS
     rmdir_test.cpp
   DEPENDS
     libc.include.errno
     libc.include.fcntl

libc/test/src/unistd/lseek_test.cpp

+//===-- Unittests for lseek -----------------------------------------------===//
+//
+// 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/fcntl/open.h"
+#include "src/unistd/close.h"
+#include "src/unistd/lseek.h"
+#include "src/unistd/read.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+#include "utils/testutils/FDReader.h"
+
+#include <errno.h>
+#include <unistd.h>
+
+TEST(LlvmLibcUniStd, LseekTest) {
+  using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+  constexpr const char *TEST_FILE = "testdata/lseek.test";
+  int fd = __llvm_libc::open(TEST_FILE, O_RDONLY);
+  ASSERT_EQ(errno, 0);
+  ASSERT_GT(fd, 0);
+  constexpr const char LSEEK_TEST[] = "lseek test";
+  constexpr int LSEEK_TEST_SIZE = sizeof(LSEEK_TEST) - 1;
+
+  char read_buf[20];
+  ASSERT_THAT(__llvm_libc::read(fd, read_buf, LSEEK_TEST_SIZE),
+              Succeeds(LSEEK_TEST_SIZE));
+  read_buf[LSEEK_TEST_SIZE] = '\0';
+  EXPECT_STREQ(read_buf, LSEEK_TEST);
+
+  // Seek to the beginning of the file and re-read.
+  ASSERT_THAT(__llvm_libc::lseek(fd, 0, SEEK_SET), Succeeds(0));
+  ASSERT_THAT(__llvm_libc::read(fd, read_buf, LSEEK_TEST_SIZE),
+              Succeeds(LSEEK_TEST_SIZE));
+  read_buf[LSEEK_TEST_SIZE] = '\0';
+  EXPECT_STREQ(read_buf, LSEEK_TEST);
+
+  // Seek to the beginning of the file from the end and re-read.
+  ASSERT_THAT(__llvm_libc::lseek(fd, -LSEEK_TEST_SIZE, SEEK_END), Succeeds(0));
+  ASSERT_THAT(__llvm_libc::read(fd, read_buf, LSEEK_TEST_SIZE),
+              Succeeds(LSEEK_TEST_SIZE));
+  read_buf[LSEEK_TEST_SIZE] = '\0';
+  EXPECT_STREQ(read_buf, LSEEK_TEST);
+
+  ASSERT_THAT(__llvm_libc::close(fd), Succeeds(0));
+}
+
+TEST(LlvmLibcUniStd, LseekFailsTest) {
+  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
+  using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+  constexpr const char *TEST_FILE = "testdata/lseek.test";
+  int fd = __llvm_libc::open(TEST_FILE, O_RDONLY);
+  ASSERT_EQ(errno, 0);
+  ASSERT_GT(fd, 0);
+  EXPECT_THAT(__llvm_libc::lseek(fd, -1, SEEK_CUR), Fails(EINVAL));
+  ASSERT_THAT(__llvm_libc::close(fd), Succeeds(0));
+}

libc/test/src/unistd/testdata/CMakeLists.txt

 # This directory will be used to create test files and delete them
 # from tests.
+
+file(GENERATE OUTPUT lseek.test CONTENT "lseek test")