Fix RISC OS not having a pread/pwrite implementation.

2 files changed, 49 insertions, 3 deletions

diff --git a/utils/config.h b/utils/config.h
index c45b865fe..cfb9d83c3 100644
--- a/utils/config.h
+++ b/utils/config.h
@@ -39,7 +39,7 @@ char *strcasestr(const char *haystack, const char *needle);
 #endif
 
 /* Although these platforms might have strftime or strptime they
- * appear not to support the time_t seconds format specifier.
+ *  appear not to support the time_t seconds format specifier.
  */
 #if (defined(_WIN32) || defined(riscos) || defined(__HAIKU__) || defined(__BEOS__) || defined(__amigaos4__) || defined(__AMIGA__) || defined(__MINT__))
 #undef HAVE_STRPTIME
@@ -49,8 +49,9 @@ char *strcasestr(const char *haystack, const char *needle);
 #define HAVE_STRFTIME
 #endif
 
-/* For some reason, UnixLib defines this unconditionally. 
- * Assume we're using UnixLib if building for RISC OS. */
+/* For some reason, UnixLib defines this unconditionally. Assume we're using
+ *  UnixLib if building for RISC OS.
+ */
 #if ((defined(_GNU_SOURCE) && !defined(__APPLE__)) || defined(riscos))
 #define HAVE_STRCHRNUL
 #else
@@ -58,6 +59,19 @@ char *strcasestr(const char *haystack, const char *needle);
 char *strchrnul(const char *s, int c);
 #endif
 
+/* Although these are in POSIX and implemented most places, RISC OS is
+ *  missing them.
+ */
+#if (defined(riscos))
+#undef HAVE_PREAD
+#undef HAVE_PWRITE
+ssize_t pread(int fd, void *buf, size_t count, off_t offset);
+ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset);
+#else
+#define HAVE_PREAD
+#define HAVE_PWRITE
+#endif
+
 #define HAVE_SYS_SELECT
 #define HAVE_INETATON
 #if (defined(_WIN32))
diff --git a/utils/utils.c b/utils/utils.c
index 5c8acd6f0..722e32302 100644
--- a/utils/utils.c
+++ b/utils/utils.c
@@ -32,6 +32,7 @@
 #include <regex.h>
 #include <time.h>
 #include <errno.h>
+#include <unistd.h>
 
 #include "utils/config.h"
 #include "utils/log.h"
@@ -628,3 +629,34 @@ nserror nsc_snptimet(char *str, size_t size, time_t *timep)
 
 	return NSERROR_OK;
 }
+
+#ifndef HAVE_PREAD
+
+ssize_t pread(int fd, void *buf, size_t count, off_t offset)
+{
+	off_t sk;
+
+	sk = lseek(fd, offset, SEEK_SET);
+	if (sk == -1) {
+		return (off_t)-1;
+	}
+	return read(fd, buf, count);
+}
+
+#endif
+
+
+#ifndef HAVE_PWRITE
+
+ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset)
+{
+	off_t sk;
+
+	sk = lseek(fd, offset, SEEK_SET);
+	if (sk == (off_t)-1) {
+		return -1;
+	}
+	return write(fd, buf, count);
+}
+
+#endif