Use ::read instead of pread in AudioSource::read_peaks for portability

This destroys the atomicity of pread() 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, 22 insertions, 10 deletions

diff --git a/libs/ardour/audiosource.cc b/libs/ardour/audiosource.cc
index 35b7da2108..776749fb57 100644
--- a/libs/ardour/audiosource.cc
+++ b/libs/ardour/audiosource.cc
@@ -370,8 +370,9 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
 
 	if (scale == 1.0) {
 
+		off_t offset = 0;
 		off_t first_peak_byte = (start / samples_per_file_peak) * sizeof (PeakData);
-
+		ssize_t bytes_to_read = sizeof (PeakData)* npeaks;
 		/* open, read, close */
 
 		if ((peakfile_fd = peakfile_descriptor->allocate ()) < 0) {
@@ -381,11 +382,16 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
 
 		DEBUG_TRACE (DEBUG::Peaks, "DIRECT PEAKS\n");
 
-#ifndef WIN32
-		nread = ::pread (peakfile_fd, peaks, sizeof (PeakData)* npeaks, first_peak_byte);
-#endif
+		offset = lseek (peakfile_fd, first_peak_byte, SEEK_SET);
+
+		if (offset != first_peak_byte) {
+			error << string_compose(_("AudioSource: could not seek to correct location in peak file \"%1\" (%2)"), peakpath, strerror (errno)) << endmsg;
+			return -1;
+		}
+
+		nread = ::read (peakfile_fd, peaks, bytes_to_read);
 
-		if (nread != sizeof (PeakData) * npeaks) {
+		if (nread != bytes_to_read) {
 			DEBUG_TRACE (DEBUG::Peaks,  string_compose ("[%1]: Cannot read peaks from peakfile! (read only %2 not %3 at sample %4 = byte %5 )\n"
 			     , _name, nread, npeaks, start, first_peak_byte));
 			return -1;
@@ -448,13 +454,20 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
 				uint32_t       start_byte = current_stored_peak * sizeof(PeakData);
 				tnp = min ((framecnt_t)(_length/samples_per_file_peak - current_stored_peak), (framecnt_t) expected_peaks);
 				to_read = min (chunksize, tnp);
+				ssize_t bytes_to_read = sizeof (PeakData) * to_read;
 
 				DEBUG_TRACE (DEBUG::Peaks, string_compose ("reading %1 bytes from peakfile @ %2\n"
-						, sizeof (PeakData) * to_read, start_byte));
+						, bytes_to_read, start_byte));
 
-#ifndef WIN32
-				if ((nread = ::pread (peakfile_fd, staging.get(), sizeof (PeakData) * to_read, start_byte))
-				    != sizeof (PeakData) * to_read) {
+
+				off_t offset = lseek (peakfile_fd, start_byte, SEEK_SET);
+
+				if (offset != start_byte) {
+					error << string_compose(_("AudioSource: could not seek to correct location in peak file \"%1\" (%2)"), peakpath, strerror (errno)) << endmsg;
+					return -1;
+				}
+
+				if ((nread = ::read (peakfile_fd, staging.get(), bytes_to_read)) != bytes_to_read) {
 
 					off_t fend = lseek (peakfile_fd, 0, SEEK_END);
 
@@ -462,7 +475,6 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
 					     , _name, (nread / sizeof(PeakData)), to_read, g_strerror (errno), start_byte, _length, fend, ((_length - current_frame)/samples_per_file_peak), npeaks));
 					return -1;
 				}
-#endif
 				i = 0;
 				stored_peaks_read = nread / sizeof(PeakData);
 			}