audiosource.cc

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/*
    Copyright (C) 2000 Paul Davis

    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 2 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, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#ifdef COMPILER_MSVC
#include <sys/utime.h>
#else
#include <unistd.h>
#include <utime.h>
#endif
#include <sys/stat.h>
#include <fcntl.h>
#include <float.h>
#include <cerrno>
#include <ctime>
#include <cmath>
#include <iomanip>
#include <fstream>
#include <algorithm>
#include <vector>

#ifdef PLATFORM_WINDOWS
#include <windows.h>

#else
#include <sys/mman.h>

#endif

#include <glib.h>
#include <glib/gstdio.h>

#include <boost/scoped_ptr.hpp>

#include <glibmm/fileutils.h>
#include <glibmm/miscutils.h>

#include "pbd/scoped_file_descriptor.h"
#include "pbd/xml++.h"

#include "ardour/audiosource.h"
#include "ardour/rc_configuration.h"
#include "ardour/runtime_functions.h"

#include "i18n.h"

#include "ardour/debug.h"

using namespace std;
using namespace ARDOUR;
using namespace PBD;

Glib::Threads::Mutex AudioSource::_level_buffer_lock;
vector<boost::shared_array<Sample> > AudioSource::_mixdown_buffers;
vector<boost::shared_array<gain_t> > AudioSource::_gain_buffers;
size_t AudioSource::_working_buffers_size = 0;
bool AudioSource::_build_missing_peakfiles = false;

bool AudioSource::_build_peakfiles = false;

#define _FPP 256

AudioSource::AudioSource (Session& s, string name)
        : Source (s, DataType::AUDIO, name)
        , _length (0)
        , _peak_byte_max (0)
        , _peaks_built (false)
        , _peakfile_fd (-1)
        , peak_leftover_cnt (0)
        , peak_leftover_size (0)
        , peak_leftovers (0)
        , _first_run (true)
        , _last_scale (0.0)
        , _last_map_off (0)
        , _last_raw_map_length (0)
{
}

AudioSource::AudioSource (Session& s, const XMLNode& node)
        : Source (s, node)
        , _length (0)
        , _peak_byte_max (0)
        , _peaks_built (false)
        , _peakfile_fd (-1)
        , peak_leftover_cnt (0)
        , peak_leftover_size (0)
        , peak_leftovers (0)
        , _first_run (true)
        , _last_scale (0.0)
        , _last_map_off (0)
        , _last_raw_map_length (0)
{
        if (set_state (node, Stateful::loading_state_version)) {
                throw failed_constructor();
        }
}

AudioSource::~AudioSource ()
{
        /* shouldn't happen but make sure we don't leak file descriptors anyway */

        if (peak_leftover_cnt) {
                cerr << "AudioSource destroyed with leftover peak data pending" << endl;
        }

        if ((-1) != _peakfile_fd) {
                close (_peakfile_fd);
                _peakfile_fd = -1;
        }

        delete [] peak_leftovers;
}

XMLNode&
AudioSource::get_state ()
{
        XMLNode& node (Source::get_state());

        if (_captured_for.length()) {
                node.add_property ("captured-for", _captured_for);
        }

        return node;
}

int
AudioSource::set_state (const XMLNode& node, int /*version*/)
{
        const XMLProperty* prop;

        if ((prop = node.property ("captured-for")) != 0) {
                _captured_for = prop->value();
        }

        return 0;
}

bool
AudioSource::empty () const
{
        return _length == 0;
}

framecnt_t
AudioSource::length (framepos_t /*pos*/) const
{
        return _length;
}

void
AudioSource::update_length (framecnt_t len)
{
        if (len > _length) {
                _length = len;
        }
}


/***********************************************************************
  PEAK FILE STUFF
 ***********************************************************************/

bool
AudioSource::peaks_ready (boost::function<void()> doThisWhenReady, ScopedConnection** connect_here_if_not, EventLoop* event_loop) const
{
        bool ret;
        Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);

        if (!(ret = _peaks_built)) {
                *connect_here_if_not = new ScopedConnection;
                PeaksReady.connect (**connect_here_if_not, MISSING_INVALIDATOR, doThisWhenReady, event_loop);
        }

        return ret;
}

void
AudioSource::touch_peakfile ()
{
        GStatBuf statbuf;

        if (g_stat (peakpath.c_str(), &statbuf) != 0 || statbuf.st_size == 0) {
                return;
        }

        struct utimbuf tbuf;

        tbuf.actime = statbuf.st_atime;
        tbuf.modtime = time ((time_t*) 0);

        g_utime (peakpath.c_str(), &tbuf);
}

int
AudioSource::rename_peakfile (string newpath)
{
        /* caller must hold _lock */

        string oldpath = peakpath;

        if (Glib::file_test (oldpath, Glib::FILE_TEST_EXISTS)) {
                if (g_rename (oldpath.c_str(), newpath.c_str()) != 0) {
                        error << string_compose (_("cannot rename peakfile for %1 from %2 to %3 (%4)"), _name, oldpath, newpath, strerror (errno)) << endmsg;
                        return -1;
                }
        }

        peakpath = newpath;

        return 0;
}

int
AudioSource::initialize_peakfile (string audio_path)
{
        GStatBuf statbuf;

        peakpath = peak_path (audio_path);

        DEBUG_TRACE(DEBUG::Peaks, string_compose ("Initialize Peakfile %1 for Audio file %2\n", peakpath, audio_path));

        /* if the peak file should be there, but isn't .... */

        if (!empty() && !Glib::file_test (peakpath.c_str(), Glib::FILE_TEST_EXISTS)) {
                peakpath = find_broken_peakfile (peakpath, audio_path);
        }

        if (g_stat (peakpath.c_str(), &statbuf)) {
                if (errno != ENOENT) {
                        /* it exists in the peaks dir, but there is some kind of error */

                        error << string_compose(_("AudioSource: cannot stat peakfile \"%1\""), peakpath) << endmsg;
                        return -1;
                }

                DEBUG_TRACE(DEBUG::Peaks, string_compose("Peakfile %1 does not exist\n", peakpath));

                _peaks_built = false;

        } else {

                /* we found it in the peaks dir, so check it out */

                if (statbuf.st_size == 0 || (statbuf.st_size < (off_t) ((length(_timeline_position) / _FPP) * sizeof (PeakData)))) {
                        DEBUG_TRACE(DEBUG::Peaks, string_compose("Peakfile %1 is empty\n", peakpath));
                        _peaks_built = false;
                } else {
                        // Check if the audio file has changed since the peakfile was built.
                        struct stat stat_file;
                        int err = stat (audio_path.c_str(), &stat_file);

                        if (err) {

                                /* no audio path - nested source or we can't
                                   read it or ... whatever, use the peakfile as-is.
                                */
                                DEBUG_TRACE(DEBUG::Peaks, string_compose("Error when calling stat on Peakfile %1\n", peakpath));

                                _peaks_built = true;
                                _peak_byte_max = statbuf.st_size;

                        } else {

                                /* allow 6 seconds slop on checking peak vs. file times because of various
                                   disk action "races"
                                */

                                if (stat_file.st_mtime > statbuf.st_mtime && (stat_file.st_mtime - statbuf.st_mtime > 6)) {
                                        _peaks_built = false;
                                        _peak_byte_max = 0;
                                } else {
                                        _peaks_built = true;
                                        _peak_byte_max = statbuf.st_size;
                                }
                        }
                }
        }

        if (!empty() && !_peaks_built && _build_missing_peakfiles && _build_peakfiles) {
                build_peaks_from_scratch ();
        }

        return 0;
}

framecnt_t
AudioSource::read (Sample *dst, framepos_t start, framecnt_t cnt, int /*channel*/) const
{
        assert (cnt >= 0);
        
        Glib::Threads::Mutex::Lock lm (_lock);
        return read_unlocked (dst, start, cnt);
}

framecnt_t
AudioSource::write (Sample *dst, framecnt_t cnt)
{
        Glib::Threads::Mutex::Lock lm (_lock);
        /* any write makes the file not removable */
        _flags = Flag (_flags & ~Removable);
        return write_unlocked (dst, cnt);
}

int
AudioSource::read_peaks (PeakData *peaks, framecnt_t npeaks, framepos_t start, framecnt_t cnt, double samples_per_visual_peak) const
{
        return read_peaks_with_fpp (peaks, npeaks, start, cnt, samples_per_visual_peak, _FPP);
}

int
AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t start, framecnt_t cnt,
                                  double samples_per_visual_peak, framecnt_t samples_per_file_peak) const
{
        Glib::Threads::Mutex::Lock lm (_lock);
        double scale;
        double expected_peaks;
        PeakData::PeakDatum xmax;
        PeakData::PeakDatum xmin;
        int32_t to_read;
#ifdef PLATFORM_WINDOWS
        SYSTEM_INFO system_info;
        GetSystemInfo (&system_info);
        const int bufsize = system_info.dwAllocationGranularity;;
#else
        const int bufsize = sysconf(_SC_PAGESIZE);
#endif
        framecnt_t read_npeaks = npeaks;
        framecnt_t zero_fill = 0;

        ScopedFileDescriptor sfd (::open (peakpath.c_str(), O_RDONLY));

        if (sfd < 0) {
                error << string_compose (_("Cannot open peakfile @ %1 for reading (%2)"), peakpath, strerror (errno)) << endmsg;
                return -1;
        }
                                  
        expected_peaks = (cnt / (double) samples_per_file_peak);
        scale = npeaks/expected_peaks;

        DEBUG_TRACE (DEBUG::Peaks, string_compose (" ======>RP: npeaks = %1 start = %2 cnt = %3 len = %4 samples_per_visual_peak = %5 expected was %6 ... scale =  %7 PD ptr = %8\n"
                        , npeaks, start, cnt, _length, samples_per_visual_peak, expected_peaks, scale, peaks));

        /* fix for near-end-of-file conditions */

        if (cnt > _length - start) {
                // cerr << "too close to end @ " << _length << " given " << start << " + " << cnt << " (" << _length - start << ")" << endl;
                cnt = _length - start;
                read_npeaks = min ((framecnt_t) floor (cnt / samples_per_visual_peak), npeaks);
                zero_fill = npeaks - read_npeaks;
        }

        // cerr << "actual npeaks = " << read_npeaks << " zf = " << zero_fill << endl;

        if (npeaks == cnt) {

                DEBUG_TRACE (DEBUG::Peaks, "RAW DATA\n");

                /* no scaling at all, just get the sample data and duplicate it for
                   both max and min peak values.
                */

                boost::scoped_array<Sample> raw_staging(new Sample[cnt]);

                if (read_unlocked (raw_staging.get(), start, cnt) != cnt) {
                        error << _("cannot read sample data for unscaled peak computation") << endmsg;
                        return -1;
                }

                for (framecnt_t i = 0; i < npeaks; ++i) {
                        peaks[i].max = raw_staging[i];
                        peaks[i].min = raw_staging[i];
                }

                return 0;
        }

        if (scale == 1.0) {
                off_t first_peak_byte = (start / samples_per_file_peak) * sizeof (PeakData);
                size_t bytes_to_read = sizeof (PeakData) * read_npeaks;
                /* open, read, close */

                DEBUG_TRACE (DEBUG::Peaks, "DIRECT PEAKS\n");

                off_t  map_off =  first_peak_byte;
                off_t  read_map_off = map_off & ~(bufsize - 1);
                off_t  map_delta = map_off - read_map_off;
                size_t map_length = bytes_to_read + map_delta;

                if (_first_run  || (_last_scale != samples_per_visual_peak) || (_last_map_off != map_off) || (_last_raw_map_length  < bytes_to_read)) {
                        peak_cache.reset (new PeakData[npeaks]);
                        char* addr;
#ifdef PLATFORM_WINDOWS
                        HANDLE file_handle = (HANDLE) _get_osfhandle(int(sfd));
                        HANDLE map_handle;
                        LPVOID view_handle;
                        bool err_flag;

                        map_handle = CreateFileMapping(file_handle, NULL, PAGE_READONLY, 0, 0, NULL);
                        if (map_handle == NULL) {
                                error << string_compose (_("map failed - could not create file mapping for peakfile %1."), peakpath) << endmsg;
                                return -1;
                        }

                        view_handle = MapViewOfFile(map_handle, FILE_MAP_READ, 0, read_map_off, map_length);
                        if (view_handle == NULL) {
                                error << string_compose (_("map failed - could not map peakfile %1."), peakpath) << endmsg;
                                return -1;
                        }

                        addr = (char*) view_handle;

                        memcpy ((void*)peak_cache.get(), (void*)(addr + map_delta), bytes_to_read);

                        err_flag = UnmapViewOfFile (view_handle);
                        err_flag = CloseHandle(map_handle);
                        if(!err_flag) {
                                error << string_compose (_("unmap failed - could not unmap peakfile %1."), peakpath) << endmsg;
                                return -1;
                        }
#else
                        addr = (char*) mmap (0, map_length, PROT_READ, MAP_PRIVATE, sfd, read_map_off);
                        if (addr ==  MAP_FAILED) {
                                error << string_compose (_("map failed - could not mmap peakfile %1."), peakpath) << endmsg;
                                return -1;
                        }

                        memcpy ((void*)peak_cache.get(), (void*)(addr + map_delta), bytes_to_read);
                        munmap (addr, map_length);
#endif
                        if (zero_fill) {
                                memset (&peak_cache[read_npeaks], 0, sizeof (PeakData) * zero_fill);
                        }

                        _first_run = false;
                        _last_scale = samples_per_visual_peak;
                        _last_map_off = map_off;
                        _last_raw_map_length = bytes_to_read;
                }

                memcpy ((void*)peaks, (void*)peak_cache.get(), npeaks * sizeof(PeakData));

                return 0;
        }

        if (scale < 1.0) {

                DEBUG_TRACE (DEBUG::Peaks, "DOWNSAMPLE\n");

                /* the caller wants:

                    - more frames-per-peak (lower resolution) than the peakfile, or to put it another way,
                    - less peaks than the peakfile holds for the same range

                    So, read a block into a staging area, and then downsample from there.

                    to avoid confusion, I'll refer to the requested peaks as visual_peaks and the peakfile peaks as stored_peaks
                */

                const framecnt_t chunksize = (framecnt_t) expected_peaks; // we read all the peaks we need in one hit.

                /* compute the rounded up frame position  */

                framepos_t current_stored_peak = (framepos_t) ceil (start / (double) samples_per_file_peak);
                framepos_t next_visual_peak  = (framepos_t) ceil (start / samples_per_visual_peak);
                double     next_visual_peak_frame = next_visual_peak * samples_per_visual_peak;
                framepos_t stored_peak_before_next_visual_peak = (framepos_t) next_visual_peak_frame / samples_per_file_peak;
                framecnt_t nvisual_peaks = 0;
                uint32_t i = 0;

                /* handle the case where the initial visual peak is on a pixel boundary */

                current_stored_peak = min (current_stored_peak, stored_peak_before_next_visual_peak);

                /* open ... close during out: handling */

                off_t  map_off =  (uint32_t) (ceil (start / (double) samples_per_file_peak)) * sizeof(PeakData);
                off_t  read_map_off = map_off & ~(bufsize - 1);
                off_t  map_delta = map_off - read_map_off;
                size_t raw_map_length = chunksize * sizeof(PeakData);
                size_t map_length = (chunksize * sizeof(PeakData)) + map_delta;

                if (_first_run || (_last_scale != samples_per_visual_peak) || (_last_map_off != map_off) || (_last_raw_map_length < raw_map_length)) {
                        peak_cache.reset (new PeakData[npeaks]);
                        boost::scoped_array<PeakData> staging (new PeakData[chunksize]);

                        char* addr;
#ifdef PLATFORM_WINDOWS
                        HANDLE file_handle =  (HANDLE) _get_osfhandle(int(sfd));
                        HANDLE map_handle;
                        LPVOID view_handle;
                        bool err_flag;

                        map_handle = CreateFileMapping(file_handle, NULL, PAGE_READONLY, 0, 0, NULL);
                        if (map_handle == NULL) {
                                error << string_compose (_("map failed - could not create file mapping for peakfile %1."), peakpath) << endmsg;
                                return -1;
                        }

                        view_handle = MapViewOfFile(map_handle, FILE_MAP_READ, 0, read_map_off, map_length);
                        if (view_handle == NULL) {
                                error << string_compose (_("map failed - could not map peakfile %1."), peakpath) << endmsg;
                                return -1;
                        }

                        addr = (char *) view_handle;

                        memcpy ((void*)staging.get(), (void*)(addr + map_delta), raw_map_length);

                        err_flag = UnmapViewOfFile (view_handle);
                        err_flag = CloseHandle(map_handle);
                        if(!err_flag) {
                                error << string_compose (_("unmap failed - could not unmap peakfile %1."), peakpath) << endmsg;
                                return -1;
                        }
#else
                        addr = (char*) mmap (0, map_length, PROT_READ, MAP_PRIVATE, sfd, read_map_off);
                        if (addr ==  MAP_FAILED) {
                                error << string_compose (_("map failed - could not mmap peakfile %1."), peakpath) << endmsg;
                                return -1;
                        }

                        memcpy ((void*)staging.get(), (void*)(addr + map_delta), raw_map_length);
                        munmap (addr, map_length);
#endif
                        while (nvisual_peaks < read_npeaks) {

                                xmax = -1.0;
                                xmin = 1.0;

                                while ((current_stored_peak <= stored_peak_before_next_visual_peak) && (i < chunksize)) {

                                        xmax = max (xmax, staging[i].max);
                                        xmin = min (xmin, staging[i].min);
                                        ++i;
                                        ++current_stored_peak;
                                }

                                peak_cache[nvisual_peaks].max = xmax;
                                peak_cache[nvisual_peaks].min = xmin;
                                ++nvisual_peaks;
                                next_visual_peak_frame =  min ((double) start + cnt, (next_visual_peak_frame + samples_per_visual_peak));
                                stored_peak_before_next_visual_peak = (uint32_t) next_visual_peak_frame / samples_per_file_peak;
                        }

                        if (zero_fill) {
                                cerr << "Zero fill end of peaks (@ " << read_npeaks << " with " << zero_fill << ")" << endl;
                                memset (&peak_cache[read_npeaks], 0, sizeof (PeakData) * zero_fill);
                        }

                        _first_run = false;
                        _last_scale = samples_per_visual_peak;
                        _last_map_off = map_off;
                        _last_raw_map_length = raw_map_length;
                }

                memcpy ((void*)peaks, (void*)peak_cache.get(), npeaks * sizeof(PeakData));

        } else {
                DEBUG_TRACE (DEBUG::Peaks, "UPSAMPLE\n");

                /* the caller wants

                     - less frames-per-peak (more resolution)
                     - more peaks than stored in the Peakfile

                   So, fetch data from the raw source, and generate peak
                   data on the fly.
                */

                framecnt_t frames_read = 0;
                framepos_t current_frame = start;
                framecnt_t i = 0;
                framecnt_t nvisual_peaks = 0;
                framecnt_t chunksize = (framecnt_t) min (cnt, (framecnt_t) 4096);
                boost::scoped_array<Sample> raw_staging(new Sample[chunksize]);

                framepos_t frame_pos = start;
                double pixel_pos = floor (frame_pos / samples_per_visual_peak);
                double next_pixel_pos = ceil (frame_pos / samples_per_visual_peak);
                double pixels_per_frame = 1.0 / samples_per_visual_peak;

                xmin = 1.0;
                xmax = -1.0;

                while (nvisual_peaks < read_npeaks) {

                        if (i == frames_read) {

                                to_read = min (chunksize, (framecnt_t)(_length - current_frame));

                                if (current_frame >= _length) {

                                        /* hmm, error condition - we've reached the end of the file
                                           without generating all the peak data. cook up a zero-filled
                                           data buffer and then use it. this is simpler than
                                           adjusting zero_fill and read_npeaks and then breaking out of
                                           this loop early
                                        */

                                        memset (raw_staging.get(), 0, sizeof (Sample) * chunksize);

                                } else {

                                        to_read = min (chunksize, (_length - current_frame));


                                        if ((frames_read = read_unlocked (raw_staging.get(), current_frame, to_read)) == 0) {
                                                error << string_compose(_("AudioSource[%1]: peak read - cannot read %2 samples at offset %3 of %4 (%5)"),
                                                                        _name, to_read, current_frame, _length, strerror (errno))
                                                      << endmsg;
                                                return -1;
                                        }
                                }

                                i = 0;
                        }

                        xmax = max (xmax, raw_staging[i]);
                        xmin = min (xmin, raw_staging[i]);
                        ++i;
                        ++current_frame;
                        pixel_pos += pixels_per_frame;

                        if (pixel_pos >= next_pixel_pos) {

                                peaks[nvisual_peaks].max = xmax;
                                peaks[nvisual_peaks].min = xmin;
                                ++nvisual_peaks;
                                xmin = 1.0;
                                xmax = -1.0;

                                next_pixel_pos = ceil (pixel_pos + 0.5);
                        }
                }

                if (zero_fill) {
                        memset (&peaks[read_npeaks], 0, sizeof (PeakData) * zero_fill);
                }
        }

        DEBUG_TRACE (DEBUG::Peaks, "READPEAKS DONE\n");
        return 0;
}

int
AudioSource::build_peaks_from_scratch ()
{
        const framecnt_t bufsize = 65536; // 256kB per disk read for mono data is about ideal

        DEBUG_TRACE (DEBUG::Peaks, "Building peaks from scratch\n");

        int ret = -1;

        {
                /* hold lock while building peaks */

                Glib::Threads::Mutex::Lock lp (_lock);

                if (prepare_for_peakfile_writes ()) {
                        goto out;
                }

                framecnt_t current_frame = 0;
                framecnt_t cnt = _length;

                _peaks_built = false;
                boost::scoped_array<Sample> buf(new Sample[bufsize]);

                while (cnt) {

                        framecnt_t frames_to_read = min (bufsize, cnt);
                        framecnt_t frames_read;
                        
                        if ((frames_read = read_unlocked (buf.get(), current_frame, frames_to_read)) != frames_to_read) {
                                error << string_compose(_("%1: could not write read raw data for peak computation (%2)"), _name, strerror (errno)) << endmsg;
                                done_with_peakfile_writes (false);
                                goto out;
                        }

                        if (compute_and_write_peaks (buf.get(), current_frame, frames_read, true, false, _FPP)) {
                                break;
                        }

                        current_frame += frames_read;
                        cnt -= frames_read;
                }

                if (cnt == 0) {
                        /* success */
                        truncate_peakfile();
                }

                done_with_peakfile_writes ((cnt == 0));
                if (cnt == 0) {
                        ret = 0;
                }
        }

  out:
        if (ret) {
                DEBUG_TRACE (DEBUG::Peaks, string_compose("Could not write peak data, attempting to remove peakfile %1\n", peakpath));
                ::g_unlink (peakpath.c_str());
        }

        return ret;
}

int
AudioSource::prepare_for_peakfile_writes ()
{
        if ((_peakfile_fd = open (peakpath.c_str(), O_CREAT|O_RDWR, 0664)) < 0) {
                error << string_compose(_("AudioSource: cannot open peakpath (c) \"%1\" (%2)"), peakpath, strerror (errno)) << endmsg;
                return -1;
        }
        return 0;
}

void
AudioSource::done_with_peakfile_writes (bool done)
{
        if (peak_leftover_cnt) {
                compute_and_write_peaks (0, 0, 0, true, false, _FPP);
        }

        if (done) {
                Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);
                _peaks_built = true;
                PeaksReady (); /* EMIT SIGNAL */
        }

        close (_peakfile_fd);
        _peakfile_fd = -1;
}

int
AudioSource::compute_and_write_peaks (Sample* buf, framecnt_t first_frame, framecnt_t cnt,
                                      bool force, bool intermediate_peaks_ready)
{
        return compute_and_write_peaks (buf, first_frame, cnt, force, intermediate_peaks_ready, _FPP);
}

int
AudioSource::compute_and_write_peaks (Sample* buf, framecnt_t first_frame, framecnt_t cnt,
                                      bool force, bool intermediate_peaks_ready, framecnt_t fpp)
{
        framecnt_t to_do;
        uint32_t  peaks_computed;
        framepos_t current_frame;
        framecnt_t frames_done;
        const size_t blocksize = (128 * 1024);
        off_t first_peak_byte;
        boost::scoped_array<Sample> buf2;

        if (_peakfile_fd < 0) {
                if (prepare_for_peakfile_writes ()) {
                        return -1;
                }
        }

  restart:
        if (peak_leftover_cnt) {

                if (first_frame != peak_leftover_frame + peak_leftover_cnt) {

                        /* uh-oh, ::seek() since the last ::compute_and_write_peaks(),
                           and we have leftovers. flush a single peak (since the leftovers
                           never represent more than that, and restart.
                        */

                        PeakData x;

                        x.min = peak_leftovers[0];
                        x.max = peak_leftovers[0];

                        off_t byte = (peak_leftover_frame / fpp) * 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;
                        }

                        _peak_byte_max = max (_peak_byte_max, (off_t) (byte + sizeof(PeakData)));

                        {
                                Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);
                                PeakRangeReady (peak_leftover_frame, peak_leftover_cnt); /* EMIT SIGNAL */
                                if (intermediate_peaks_ready) {
                                        PeaksReady (); /* EMIT SIGNAL */
                                }
                        }

                        /* left overs are done */

                        peak_leftover_cnt = 0;
                        goto restart;
                }

                /* else ... had leftovers, but they immediately preceed the new data, so just
                   merge them and compute.
                */

                /* make a new contiguous buffer containing leftovers and the new stuff */

                to_do = cnt + peak_leftover_cnt;
                buf2.reset(new Sample[to_do]);

                /* the remnants */
                memcpy (buf2.get(), peak_leftovers, peak_leftover_cnt * sizeof (Sample));

                /* the new stuff */
                memcpy (buf2.get()+peak_leftover_cnt, buf, cnt * sizeof (Sample));

                /* no more leftovers */
                peak_leftover_cnt = 0;

                /* use the temporary buffer */
                buf = buf2.get();

                /* make sure that when we write into the peakfile, we startup where we left off */

                first_frame = peak_leftover_frame;

        } else {
                to_do = cnt;
        }

        boost::scoped_array<PeakData> peakbuf(new PeakData[(to_do/fpp)+1]);
        peaks_computed = 0;
        current_frame = first_frame;
        frames_done = 0;

        while (to_do) {

                /* if some frames were passed in (i.e. we're not flushing leftovers)
                   and there are less than fpp to do, save them till
                   next time
                */

                if (force && (to_do < fpp)) {
                        /* keep the left overs around for next time */

                        if (peak_leftover_size < to_do) {
                                delete [] peak_leftovers;
                                peak_leftovers = new Sample[to_do];
                                peak_leftover_size = to_do;
                        }
                        memcpy (peak_leftovers, buf, to_do * sizeof (Sample));
                        peak_leftover_cnt = to_do;
                        peak_leftover_frame = current_frame;

                        /* done for now */

                        break;
                }

                framecnt_t this_time = min (fpp, to_do);

                peakbuf[peaks_computed].max = buf[0];
                peakbuf[peaks_computed].min = buf[0];

                ARDOUR::find_peaks (buf+1, this_time-1, &peakbuf[peaks_computed].min, &peakbuf[peaks_computed].max);

                peaks_computed++;
                buf += this_time;
                to_do -= this_time;
                frames_done += this_time;
                current_frame += this_time;
        }

        first_peak_byte = (first_frame / fpp) * sizeof (PeakData);

        if (can_truncate_peaks()) {

                /* on some filesystems (ext3, at least) this helps to reduce fragmentation of
                   the peakfiles. its not guaranteed to do so, and even on ext3 (as of december 2006)
                   it does not cause single-extent allocation even for peakfiles of
                   less than BLOCKSIZE bytes.  only call ftruncate if we'll make the file larger.
                */

                off_t endpos = lseek (_peakfile_fd, 0, SEEK_END);
                off_t target_length = blocksize * ((first_peak_byte + blocksize + 1) / blocksize);

                if (endpos < target_length) {
                        DEBUG_TRACE(DEBUG::Peaks, string_compose ("Truncating Peakfile %1\n", peakpath));
                        if (ftruncate (_peakfile_fd, target_length)) {
                                /* error doesn't actually matter so continue on without testing */
                        }
                }
        }


        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;
        }

        _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);
                PeakRangeReady (first_frame, frames_done); /* EMIT SIGNAL */
                if (intermediate_peaks_ready) {
                        PeaksReady (); /* EMIT SIGNAL */
                }
        }

        return 0;
}

void
AudioSource::truncate_peakfile ()
{
        if (_peakfile_fd < 0) {
                error << string_compose (_("programming error: %1"), "AudioSource::truncate_peakfile() called without open peakfile descriptor")
                      << endmsg;
                return;
        }

        /* truncate the peakfile down to its natural length if necessary */

        off_t end = lseek (_peakfile_fd, 0, SEEK_END);

        if (end > _peak_byte_max) {
                DEBUG_TRACE(DEBUG::Peaks, string_compose ("Truncating Peakfile  %1\n", peakpath));
                if (ftruncate (_peakfile_fd, _peak_byte_max)) {
                        error << string_compose (_("could not truncate peakfile %1 to %2 (error: %3)"),
                                                 peakpath, _peak_byte_max, errno) << endmsg;
                }
        }
}

framecnt_t
AudioSource::available_peaks (double zoom_factor) const
{
        if (zoom_factor < _FPP) {
                return length(_timeline_position); // peak data will come from the audio file
        }

        /* peak data comes from peakfile, but the filesize might not represent
           the valid data due to ftruncate optimizations, so use _peak_byte_max state.
           XXX - there might be some atomicity issues here, we should probably add a lock,
           but _peak_byte_max only monotonically increases after initialization.
        */

        off_t end = _peak_byte_max;

        return (end/sizeof(PeakData)) * _FPP;
}

void
AudioSource::mark_streaming_write_completed (const Lock& lock)
{
        Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);

        if (_peaks_built) {
                PeaksReady (); /* EMIT SIGNAL */
        }
}

void
AudioSource::allocate_working_buffers (framecnt_t framerate)
{
        Glib::Threads::Mutex::Lock lm (_level_buffer_lock);


        /* Note: we don't need any buffers allocated until
           a level 1 audiosource is created, at which
           time we'll call ::ensure_buffers_for_level()
           with the right value and do the right thing.
        */

        if (!_mixdown_buffers.empty()) {
                ensure_buffers_for_level_locked ( _mixdown_buffers.size(), framerate);
        }
}

void
AudioSource::ensure_buffers_for_level (uint32_t level, framecnt_t frame_rate)
{
        Glib::Threads::Mutex::Lock lm (_level_buffer_lock);
        ensure_buffers_for_level_locked (level, frame_rate);
}

void
AudioSource::ensure_buffers_for_level_locked (uint32_t level, framecnt_t frame_rate)
{
        framecnt_t nframes = (framecnt_t) floor (Config->get_audio_playback_buffer_seconds() * frame_rate);

        /* this may be called because either "level" or "frame_rate" have
         * changed. and it may be called with "level" smaller than the current
         * number of buffers, because a new compound region has been created at
         * a more shallow level than the deepest one we currently have.
         */

        uint32_t limit = max ((size_t) level, _mixdown_buffers.size());

        _mixdown_buffers.clear ();
        _gain_buffers.clear ();

        for (uint32_t n = 0; n < limit; ++n) {
                _mixdown_buffers.push_back (boost::shared_array<Sample> (new Sample[nframes]));
                _gain_buffers.push_back (boost::shared_array<gain_t> (new gain_t[nframes]));
        }
}