[nasm:elfmerge] nasmlib: allow writing of sparse files

[nasm-bot f. H. P. A. <hp...@li...>]

Commit-ID:  e65e81b172ceed17621c0f0ca4392a531018071e
Gitweb:     http://repo.or.cz/w/nasm.git?a=commitdiff;h=e65e81b172ceed17621c0f0ca4392a531018071e
Author:     H. Peter Anvin <hp...@li...>
AuthorDate: Thu, 18 Feb 2016 14:24:40 -0800
Committer:  H. Peter Anvin <hp...@li...>
CommitDate: Thu, 18 Feb 2016 14:24:40 -0800

nasmlib: allow writing of sparse files

On systems that support it, allow the writing of sparse files.
This can be useful for some file formats (like binary, or ELF if the
alignments are very large) that can contain large amounts of zeroes.

This is not inherently portable code, so condition it on certain known
systems.

Signed-off-by: H. Peter Anvin <hp...@li...>


---
 configure.in |  8 ++++++++
 nasmlib.c    | 29 ++++++++++++++++++++++++++++-
 nasmlib.h    |  8 +++++++-
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/configure.in b/configure.in
index e762777..98e151c 100644
--- a/configure.in
+++ b/configure.in
@@ -111,6 +111,9 @@ AC_CHECK_HEADERS(strings.h)
 dnl Look for <stdbool.h>
 AC_HEADER_STDBOOL
 
+dnl Look for <io.h>
+AC_CHECK_HEADERS(io.h)
+
 dnl Look for <unistd.h>
 AC_CHECK_HEADERS(unistd.h)
 
@@ -135,6 +138,11 @@ AC_CHECK_FUNCS(canonicalize_file_name)
 AC_CHECK_FUNCS(_fullpath)
 AC_CHECK_FUNCS(pathconf)
 
+AC_TYPE_OFF_T
+AC_FUNC_FSEEKO
+AC_CHECK_FUNCS([ftruncate _chsize _chsize_s])
+AC_CHECK_FUNCS([fileno])
+
 PA_HAVE_FUNC(__builtin_ctz, (0U))
 PA_HAVE_FUNC(__builtin_ctzl, (0UL))
 PA_HAVE_FUNC(__builtin_ctzll, (0ULL))
diff --git a/nasmlib.c b/nasmlib.c
index 49f1e47..eb0217d 100644
--- a/nasmlib.c
+++ b/nasmlib.c
@@ -165,7 +165,7 @@ no_return nasm_assert_failed(const char *file, int line, const char *msg)
 void nasm_write(const void *ptr, size_t size, FILE *f)
 {
     size_t n = fwrite(ptr, 1, size, f);
-    if (n != size)
+    if (n != size || ferror(f) || feof(f))
         nasm_error(ERR_FATAL, "unable to write output: %s", strerror(errno));
 }
 
@@ -459,10 +459,37 @@ void fwriteaddr(uint64_t data, int size, FILE * fp)
 
 #endif
 
+#ifndef HAVE_FSEEKO
+# define fseeko fseek
+# define ftello ftell
+#endif
+
+#ifdef HAVE_FILENO		/* Useless without fileno() */
+# ifdef HAVE__CHSIZE_S
+#  define nasm_ftruncate(fd,size) _chsize_s(fd,size)
+# elif defined(HAVE__CHSIZE)
+#  define nasm_ftruncate(fd,size) _chsize(fd,size)
+# elif defined(HAVE_FTRUNCATE)
+#  define nasm_ftruncate(fd,size) ftruncate(fd,size)
+# endif
+#endif
+
 void fwritezero(size_t bytes, FILE *fp)
 {
     size_t blksize;
 
+#ifdef nasm_ftruncate
+    if (bytes >= BUFSIZ && !ferror(fp) && !feof(fp)) {
+	off_t pos = ftello(fp);
+	if (pos >= 0) {
+	    if (!fflush(fp) &&
+		!nasm_ftruncate(fileno(fp), pos + bytes) &&
+		!fseeko(fp, pos+bytes, SEEK_SET))
+		    return;
+	}
+    }
+#endif
+
     while (bytes) {
 	blksize = (bytes < ZERO_BUF_SIZE) ? bytes : ZERO_BUF_SIZE;
 
diff --git a/nasmlib.h b/nasmlib.h
index 96c488a..534324d 100644
--- a/nasmlib.h
+++ b/nasmlib.h
@@ -44,7 +44,13 @@
 #include <stdio.h>
 #include <string.h>
 #ifdef HAVE_STRINGS_H
-#include <strings.h>
+# include <strings.h>
+#endif
+#ifdef HAVE_IO_H
+# include <io.h>
+#endif
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
 #endif
 
 /*