[PATCH 1/2] copy-file-range: new module

[Paul Eggert]

* MODULES.html.sh: Add copy-file-range.
* lib/copy-file-range.c, m4/copy-file-range.m4:
* modules/copy-file-range: New files.
* lib/unistd.in.h (copy_file_range): Declare.
* m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS):
Set up GNULIB_COPY_FILE_RANGE and HAVE_COPY_FILE_RANGE.
* modules/unistd (unistd.h): Substitute them.
---
 ChangeLog               |  11 +++
 MODULES.html.sh         |   1 +
 lib/copy-file-range.c   | 165 ++++++++++++++++++++++++++++++++++++++++
 lib/unistd.in.h         |  18 +++++
 m4/copy-file-range.m4   |  18 +++++
 m4/unistd_h.m4          |   4 +-
 modules/copy-file-range |  33 ++++++++
 modules/unistd          |   2 +
 8 files changed, 251 insertions(+), 1 deletion(-)
 create mode 100644 lib/copy-file-range.c
 create mode 100644 m4/copy-file-range.m4
 create mode 100644 modules/copy-file-range

diff --git a/ChangeLog b/ChangeLog
index 5e1e69ce3..9ff35e9c1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2019-06-04  Paul Eggert  <address@hidden>
+
+       copy-file-range: new module
+       * MODULES.html.sh: Add copy-file-range.
+       * lib/copy-file-range.c, m4/copy-file-range.m4:
+       * modules/copy-file-range: New files.
+       * lib/unistd.in.h (copy_file_range): Declare.
+       * m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS):
+       Set up GNULIB_COPY_FILE_RANGE and HAVE_COPY_FILE_RANGE.
+       * modules/unistd (unistd.h): Substitute them.
+
 2019-05-28  Bruno Haible  <address@hidden>
 
        binary-io: Attempted use of O_BINARY on consoles no longer fails.
diff --git a/MODULES.html.sh b/MODULES.html.sh
index 78b6d4918..80f0c2973 100755
--- a/MODULES.html.sh
+++ b/MODULES.html.sh
@@ -2735,6 +2735,7 @@ func_all_modules ()
 
   func_begin_table
   func_module binary-io
+  func_module copy-file-range
   func_module dup3
   func_module fcntl-safer
   func_module fd-safer-flag
diff --git a/lib/copy-file-range.c b/lib/copy-file-range.c
new file mode 100644
index 000000000..a1448d0d9
--- /dev/null
+++ b/lib/copy-file-range.c
@@ -0,0 +1,165 @@
+/* Emulation of copy_file_range.
+   Copyright 2017-2019 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* This file is adapted from glibc io/copy_file_range-compat.c, with a
+   small number of changes to port to non-glibc platforms.  */
+
+#include <libc-config.h>
+
+/* The following macros should be defined:
+
+   COPY_FILE_RANGE_DECL   Declaration specifiers for the function below.
+   COPY_FILE_RANGE        Name of the function to define.  */
+
+#define COPY_FILE_RANGE_DECL
+#define COPY_FILE_RANGE copy_file_range
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+COPY_FILE_RANGE_DECL
+ssize_t
+COPY_FILE_RANGE (int infd, off_t *pinoff,
+                 int outfd, off_t *poutoff,
+                 size_t length, unsigned int flags)
+{
+  if (flags != 0)
+    {
+      __set_errno (EINVAL);
+      return -1;
+    }
+
+  {
+    struct stat instat;
+    struct stat outstat;
+    if (fstat (infd, &instat) != 0 || fstat (outfd, &outstat) != 0)
+      return -1;
+    if (S_ISDIR (instat.st_mode) || S_ISDIR (outstat.st_mode))
+      {
+        __set_errno (EISDIR);
+        return -1;
+      }
+    if (!S_ISREG (instat.st_mode) || !S_ISREG (outstat.st_mode))
+      {
+        /* We need a regular input file so that the we can seek
+           backwards in case of a write failure.  */
+        __set_errno (EINVAL);
+        return -1;
+      }
+    if (instat.st_dev != outstat.st_dev)
+      {
+        /* Cross-device copies are not supported.  */
+        __set_errno (EXDEV);
+        return -1;
+      }
+  }
+
+  /* The output descriptor must not have O_APPEND set.  */
+  {
+    int flags = fcntl (outfd, F_GETFL);
+    if (flags & O_APPEND)
+      {
+        __set_errno (EBADF);
+        return -1;
+      }
+  }
+
+  /* Avoid an overflow in the result.  */
+  if (length > SSIZE_MAX)
+    length = SSIZE_MAX;
+
+  /* Main copying loop.  The buffer size is arbitrary and is a
+     trade-off between stack size consumption, cache usage, and
+     amortization of system call overhead.  */
+  size_t copied = 0;
+  char buf[8192];
+  while (length > 0)
+    {
+      size_t to_read = length;
+      if (to_read > sizeof (buf))
+        to_read = sizeof (buf);
+
+      /* Fill the buffer.  */
+      ssize_t read_count;
+      if (pinoff == NULL)
+        read_count = read (infd, buf, to_read);
+      else
+        read_count = pread (infd, buf, to_read, *pinoff);
+      if (read_count == 0)
+        /* End of file reached prematurely.  */
+        return copied;
+      if (read_count < 0)
+        {
+          if (copied > 0)
+            /* Report the number of bytes copied so far.  */
+            return copied;
+          return -1;
+        }
+      if (pinoff != NULL)
+        *pinoff += read_count;
+
+      /* Write the buffer part which was read to the destination.  */
+      char *end = buf + read_count;
+      for (char *p = buf; p < end; )
+        {
+          ssize_t write_count;
+          if (poutoff == NULL)
+            write_count = write (outfd, p, end - p);
+          else
+            write_count = pwrite (outfd, p, end - p, *poutoff);
+          if (write_count < 0)
+            {
+              /* Adjust the input read position to match what we have
+                 written, so that the caller can pick up after the
+                 error.  */
+              size_t written = p - buf;
+              /* NB: This needs to be signed so that we can form the
+                 negative value below.  */
+              ssize_t overread = read_count - written;
+              if (pinoff == NULL)
+                {
+                  if (overread > 0)
+                    {
+                      /* We are on an error recovery path, so we
+                         cannot deal with failure here.  */
+                      int save_errno = errno;
+                      (void) lseek (infd, -overread, SEEK_CUR);
+                      __set_errno (save_errno);
+                    }
+                }
+              else /* pinoff != NULL */
+                *pinoff -= overread;
+
+              if (copied + written > 0)
+                /* Report the number of bytes copied so far.  */
+                return copied + written;
+              return -1;
+            }
+          p += write_count;
+          if (poutoff != NULL)
+            *poutoff += write_count;
+        } /* Write loop.  */
+
+      copied += read_count;
+      length -= read_count;
+    }
+  return copied;
+}
diff --git a/lib/unistd.in.h b/lib/unistd.in.h
index 0ff7396b3..9ffb2e990 100644
--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -331,6 +331,24 @@ _GL_WARN_ON_USE (close, "close does not portably work on 
sockets - "
 #endif
 
 
+#if @GNULIB_COPY_FILE_RANGE@
+# if address@hidden@
+_GL_FUNCDECL_SYS (copy_file_range, ssize_t, (int ifd, off_t *ipos,
+                                             int ofd, off_t *opos,
+                                             size_t len, unsigned flags));
+_GL_CXXALIAS_SYS (copy_file_range, ssize_t, (int ifd, off_t *ipos,
+                                             int ofd, off_t *opos,
+                                             size_t len, unsigned flags));
+# endif
+_GL_CXXALIASWARN (copy_file_range);
+#elif defined GNULIB_POSIXCHECK
+/* Assume copy_file_range is always declared.  */
+_GL_WARN_ON_USE (copy_file_range,
+                 "copy_file_range is unportable - "
+                 "use gnulib module copy_file_range for portability");
+#endif
+
+
 #if @GNULIB_DUP@
 # if @REPLACE_DUP@
 #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
diff --git a/m4/copy-file-range.m4 b/m4/copy-file-range.m4
new file mode 100644
index 000000000..edd2c4aed
--- /dev/null
+++ b/m4/copy-file-range.m4
@@ -0,0 +1,18 @@
+# copy-file-range.m4
+dnl Copyright 2019 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_COPY_FILE_RANGE],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+
+  dnl Persuade glibc <unistd.h> to declare copy_file_range.
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  AC_CHECK_FUNCS_ONCE([copy_file_range])
+  if test $ac_cv_func_copy_file_range != yes; then
+    HAVE_COPY_FILE_RANGE=0
+  fi
+])
diff --git a/m4/unistd_h.m4 b/m4/unistd_h.m4
index a04055d2a..a3b3905f8 100644
--- a/m4/unistd_h.m4
+++ b/m4/unistd_h.m4
@@ -1,4 +1,4 @@
-# unistd_h.m4 serial 74
+# unistd_h.m4 serial 75
 dnl Copyright (C) 2006-2019 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -64,6 +64,7 @@ AC_DEFUN([gl_UNISTD_H_DEFAULTS],
   GNULIB_CHDIR=0;                AC_SUBST([GNULIB_CHDIR])
   GNULIB_CHOWN=0;                AC_SUBST([GNULIB_CHOWN])
   GNULIB_CLOSE=0;                AC_SUBST([GNULIB_CLOSE])
+  GNULIB_COPY_FILE_RANGE=0;      AC_SUBST([GNULIB_COPY_FILE_RANGE])
   GNULIB_DUP=0;                  AC_SUBST([GNULIB_DUP])
   GNULIB_DUP2=0;                 AC_SUBST([GNULIB_DUP2])
   GNULIB_DUP3=0;                 AC_SUBST([GNULIB_DUP3])
@@ -113,6 +114,7 @@ AC_DEFUN([gl_UNISTD_H_DEFAULTS],
   GNULIB_WRITE=0;                AC_SUBST([GNULIB_WRITE])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_CHOWN=1;           AC_SUBST([HAVE_CHOWN])
+  HAVE_COPY_FILE_RANGE=1; AC_SUBST([HAVE_COPY_FILE_RANGE])
   HAVE_DUP2=1;            AC_SUBST([HAVE_DUP2])
   HAVE_DUP3=1;            AC_SUBST([HAVE_DUP3])
   HAVE_EUIDACCESS=1;      AC_SUBST([HAVE_EUIDACCESS])
diff --git a/modules/copy-file-range b/modules/copy-file-range
new file mode 100644
index 000000000..18742ef3b
--- /dev/null
+++ b/modules/copy-file-range
@@ -0,0 +1,33 @@
+Description:
+Copy parts of files
+
+Files:
+lib/copy-file-range.c
+m4/copy-file-range.m4
+
+Depends-on:
+c99
+inttypes-incomplete [test $HAVE_COPY_FILE_RANGE = 0]
+largefile
+libc-config         [test $HAVE_COPY_FILE_RANGE = 0]
+pread               [test $HAVE_COPY_FILE_RANGE = 0]
+pwrite              [test $HAVE_COPY_FILE_RANGE = 0]
+unistd
+
+configure.ac:
+gl_FUNC_COPY_FILE_RANGE
+if test $HAVE_COPY_FILE_RANGE = 0; then
+  AC_LIBOBJ([copy-file-range])
+fi
+gl_UNISTD_MODULE_INDICATOR([copy-file-range])
+
+Makefile.am:
+
+Include:
+<unistd.h>
+
+License:
+LGPLv2+
+
+Maintainer:
+all
diff --git a/modules/unistd b/modules/unistd
index fc1a27fe1..e29c1ad94 100644
--- a/modules/unistd
+++ b/modules/unistd
@@ -39,6 +39,7 @@ unistd.h: unistd.in.h $(top_builddir)/config.status 
$(CXXDEFS_H) $(ARG_NONNULL_H
              -e 's/@''GNULIB_CHDIR''@/$(GNULIB_CHDIR)/g' \
              -e 's/@''GNULIB_CHOWN''@/$(GNULIB_CHOWN)/g' \
              -e 's/@''GNULIB_CLOSE''@/$(GNULIB_CLOSE)/g' \
+             -e 's/@''GNULIB_COPY_FILE_RANGE''@/$(GNULIB_COPY_FILE_RANGE)/g' \
              -e 's/@''GNULIB_DUP''@/$(GNULIB_DUP)/g' \
              -e 's/@''GNULIB_DUP2''@/$(GNULIB_DUP2)/g' \
              -e 's/@''GNULIB_DUP3''@/$(GNULIB_DUP3)/g' \
@@ -89,6 +90,7 @@ unistd.h: unistd.in.h $(top_builddir)/config.status 
$(CXXDEFS_H) $(ARG_NONNULL_H
              -e 's/@''GNULIB_WRITE''@/$(GNULIB_WRITE)/g' \
              < $(srcdir)/unistd.in.h | \
          sed -e 's|@''HAVE_CHOWN''@|$(HAVE_CHOWN)|g' \
+             -e 's|@''HAVE_COPY_FILE_RANGE''@|$(HAVE_COPY_FILE_RANGE)|g' \
              -e 's|@''HAVE_DUP2''@|$(HAVE_DUP2)|g' \
              -e 's|@''HAVE_DUP3''@|$(HAVE_DUP3)|g' \
              -e 's|@''HAVE_EUIDACCESS''@|$(HAVE_EUIDACCESS)|g' \
-- 
2.17.1