Use ::write instead of pwrite in AudioSource::compute_and_write_peaks for portability

This destroys the atomicity of pwrite() and thus suggests that we should do something else to ensure
that multithread access to peakfiles (if it does in fact exist) is safe. OTOH, there may be no
such thing, since they are designed for the GUI, which is single threaded (for now)

1 files changed, 23 insertions, 7 deletions

diff --git a/libs/ardour/audiosource.cc b/libs/ardour/audiosource.cc
index 776749fb57..ff92b8977d 100644
--- a/libs/ardour/audiosource.cc
+++ b/libs/ardour/audiosource.cc
@@ -725,12 +725,18 @@ AudioSource::compute_and_write_peaks (Sample* buf, framecnt_t first_frame, frame
 
 			off_t byte = (peak_leftover_frame / fpp) * sizeof (PeakData);
 
-#ifndef WIN32
-			if (::pwrite (_peakfile_fd, &x, sizeof (PeakData), byte) != sizeof (PeakData)) {
+			off_t offset = lseek (_peakfile_fd, byte, SEEK_SET);
+
+			if (offset != byte) {
+				error << string_compose(_("%1: could not seek in peak file data (%2)"), _name, strerror (errno)) << endmsg;
+				return -1;
+			}
+
+			if (::write (_peakfile_fd, &x, sizeof (PeakData)) != sizeof (PeakData)) {
 				error << string_compose(_("%1: could not write peak file data (%2)"), _name, strerror (errno)) << endmsg;
 				return -1;
 			}
-#endif
+
 			_peak_byte_max = max (_peak_byte_max, (off_t) (byte + sizeof(PeakData)));
 
 			{
@@ -840,14 +846,24 @@ AudioSource::compute_and_write_peaks (Sample* buf, framecnt_t first_frame, frame
 		}
 	}
 
-#ifndef WIN32
-	if (::pwrite (_peakfile_fd, peakbuf.get(), sizeof (PeakData) * peaks_computed, first_peak_byte) != (ssize_t) (sizeof (PeakData) * peaks_computed)) {
+
+	off_t offset = lseek(_peakfile_fd, first_peak_byte, SEEK_SET);
+
+	if (offset != first_peak_byte) {
+		error << string_compose(_("%1: could not seek in peak file data (%2)"), _name, strerror (errno)) << endmsg;
+		return -1;
+	}
+
+	ssize_t bytes_to_write = sizeof (PeakData) * peaks_computed;
+
+	ssize_t bytes_written = ::write (_peakfile_fd, peakbuf.get(), bytes_to_write);
+
+	if (bytes_written != bytes_to_write) {
 		error << string_compose(_("%1: could not write peak file data (%2)"), _name, strerror (errno)) << endmsg;
 		return -1;
 	}
-#endif
 
-	_peak_byte_max = max (_peak_byte_max, (off_t) (first_peak_byte + sizeof(PeakData)*peaks_computed));
+	_peak_byte_max = max (_peak_byte_max, (off_t) (first_peak_byte + bytes_to_write));
 
 	if (frames_done) {
 		Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);