/** Find an arbitrary number of delimited strings at the end of a file. This
* function provides the core of our last-lines-loader implementation.
*
* @param fd File descriptor to operate on. This must be opened for reading.
*
* @param bytes Delimiter sequence.
*
* @param bytes_length Number of significant bytes in @p bytes.
*
* @param count Number of tail sequences to find.
*
* @param out Destination string array.
*/
static inline size_t
find_tail_sequences(int fd, const char* bytes, size_t bytes_length, size_t count, wxArrayString& out)
{
size_t count_added ( 0 );
/* We overlap the file reads a little to avoid splitting (and thus missing) the
delimiter sequence. */
const size_t read_overlap ( bytes_length - 1 );
const size_t read_size ( BUFSIZ );
const off_t log_length ( lseek(fd, 0, SEEK_END) );
bool have_last_pos ( false );
char buf[read_size];
off_t last_found_pos ( 0 );
off_t last_read_position ( log_length + read_overlap );
/* We read `read_size'-byte blocks of the file, starting at the end and working backwards. */
while ( count_added < count && last_read_position > 0 ) {
off_t read_position ( next_read_position(last_read_position, read_size, read_overlap) );
size_t bytes_read ( pread(fd, buf, std::min(static_cast<off_t>(read_size), last_read_position - read_position), read_position) );
/* In each block, we search for `bytes', starting at the end. */
for ( ssize_t i = bytes_read - read_overlap - 1; i >= 0; i-- ) {
if ( !strncmp((buf + i), bytes, bytes_length) ) {
off_t this_found_pos ( read_position + i );
if ( have_last_pos && count_added < count ) {
size_t line_length ( last_found_pos - this_found_pos - bytes_length );
if ( line_length > 0 ) {
char* source ( NULL );
if ( last_found_pos >= read_position + (off_t) bytes_read ) {
source = new char[ line_length + 1];
memset(source, 0, line_length + 1);
if ( pread(fd, source, line_length, this_found_pos + bytes_length) < (ssize_t) line_length ) {
wxLogWarning(_T("ChatLog::find_tail_sequences: Read-byte count less than expected"));
}
} else {
source = buf + i + bytes_length;
}
if ( strncmp(source, "##", 2) != 0 ) {
out.Insert(wxString(L'\0', 0), 0);
wxLogMessage(_T("ChatLog::find_tail_sequences: fetching write buffer for %lu bytes"), sizeof(wxChar) * (line_length + 1));
#if !defined(HAVE_WX28) || defined(SL_QT_MODE)
wxStringBufferLength outzero_buf(out[0], sizeof(wxChar) * (line_length + 1));
wxConvUTF8.ToWChar(outzero_buf, line_length, source);
outzero_buf.SetLength(line_length);
#else
wxConvUTF8.MB2WC(out[0].GetWriteBuf(sizeof(wxChar) * (line_length + 1)), source, line_length);
out[0].UngetWriteBuf(line_length);
#endif
++count_added;
}
if ( last_found_pos >= read_position + (off_t) bytes_read )
delete[] source;
if ( count_added >= count )
i = -1; /* short-circuit the `for' loop. */
}
}
last_found_pos = this_found_pos;
have_last_pos = true;
i -= bytes_length - 1;
}
}
last_read_position = read_position;
}
return count_added;
}
/** Find an arbitrary number of delimited strings at the end of a file. This
* function provides the core of our last-lines-loader implementation.
*
* @param fd File descriptor to operate on. This must be opened for reading.
*
* @param bytes Delimiter sequence.
*
* @param bytes_length Number of significant bytes in @p bytes.
*
* @param count Number of tail sequences to find.
*
* @param out Destination string array.
*/
static size_t find_tail_sequences(wxFile& fd, const char* bytes, size_t bytes_length, size_t count, wxArrayString& out)
{
size_t count_added(0);
/* We overlap the file reads a little to avoid splitting (and thus missing) the
delimiter sequence. */
const size_t read_overlap = bytes_length - 1;
const size_t read_size = BUFSIZ;
const off_t log_length = fd.SeekEnd();
bool have_last_pos = false;
char buf[read_size];
off_t last_found_pos = 0;
off_t last_read_position = log_length + read_overlap;
/* We read `read_size'-byte blocks of the file, starting at the end and working backwards. */
while (count_added < count && last_read_position > 0) {
const off_t read_position = next_read_position(last_read_position, read_size, read_overlap);
const size_t bytes_read = readblock(fd, buf, std::min(static_cast<off_t>(read_size), last_read_position - read_position), read_position);
/* In each block, we search for `bytes', starting at the end. */
for (ssize_t i = bytes_read - read_overlap - 1; i >= 0; i--) {
if (strncmp((buf + i), bytes, bytes_length) == 0) {
const off_t this_found_pos = read_position + i;
if (have_last_pos) {
const size_t line_length = last_found_pos - this_found_pos - bytes_length;
if (line_length > 0) {
char* source = NULL;
if (last_found_pos >= read_position + (off_t)bytes_read) {
source = new char[line_length + 1];
memset(source, 0, line_length + 1);
if (readblock(fd, source, line_length, this_found_pos + bytes_length) < (ssize_t)line_length) {
wxLogWarning(_T("ChatLog::find_tail_sequences: Read-byte count less than expected"));
}
} else {
source = buf + i + bytes_length;
}
source[line_length] = 0;
wxString tmp = wxString::FromUTF8(source);
out.Insert(tmp, 0);
if (last_found_pos >= read_position + (off_t)bytes_read)
delete[] source;
count_added++;
if (count_added >= count)
break;
}
}
last_found_pos = this_found_pos;
have_last_pos = true;
i -= bytes_length - 1;
}
}
last_read_position = read_position;
}
return count_added;
}
