+/* In the event of a hang-up, and if its output was on a TTY, Wget
+ redirects its output to `wget-log'.
+
+ For the convenience of reading this newly-created log, we store the
+ last several lines ("screenful", hence the choice of 24) of Wget
+ output, and dump them as context when the time comes. */
+#define SAVED_LOG_LINES 24
+
+/* log_lines is a circular buffer that stores SAVED_LOG_LINES lines of
+ output. log_line_current always points to the position in the
+ buffer that will be written to next. When log_line_current reaches
+ SAVED_LOG_LINES, it is reset to zero.
+
+ The problem here is that we'd have to either (re)allocate and free
+ strings all the time, or limit the lines to an arbitrary number of
+ characters. Instead of settling for either of these, we do both:
+ if the line is smaller than a certain "usual" line length (80 chars
+ by default), a preallocated memory is used. The rare lines that
+ are longer than 80 characters are malloc'ed and freed separately.
+ This gives good performance with minimum memory consumption and
+ fragmentation. */
+
+#define STATIC_LENGTH 80
+
+static struct log_ln {
+ char static_line[STATIC_LENGTH + 1]; /* statically allocated
+ line. */
+ char *malloced_line; /* malloc'ed line, for lines of output
+ larger than 80 characters. */
+ char *content; /* this points either to malloced_line
+ or to the appropriate static_line.
+ If this is NULL, it means the line
+ has not yet been used. */
+} log_lines[SAVED_LOG_LINES];
+
+/* The current position in the ring. */
+static int log_line_current = -1;
+
+/* Whether the most recently written line was "trailing", i.e. did not
+ finish with \n. This is an important piece of information because
+ the code is always careful to append data to trailing lines, rather
+ than create new ones. */
+static int trailing_line;
+
+\f
+#define ROT_ADVANCE(num) do { \
+ if (++num >= SAVED_LOG_LINES) \
+ num = 0; \
+} while (0)
+
+/* Free the log line index with NUM. This calls free on
+ ln->malloced_line if it's non-NULL, and it also resets
+ ln->malloced_line and ln->content to NULL. */
+
+static void
+free_log_line (int num)
+{
+ struct log_ln *ln = log_lines + num;
+ if (ln->malloced_line)
+ {
+ free (ln->malloced_line);
+ ln->malloced_line = NULL;
+ }
+ ln->content = NULL;
+}
+
+/* Append bytes in the range [start, end) to one line in the log. The
+ region is not supposed to contain newlines, except for the last
+ character (at end[-1]). */
+
+static void
+saved_append_1 (const char *start, const char *end)
+{
+ int len = end - start;
+ if (!len)
+ return;
+
+ /* First, check whether we need to append to an existing line or to
+ create a new one. */
+ if (!trailing_line)
+ {
+ /* Create a new line. */
+ struct log_ln *ln;
+
+ if (log_line_current == -1)
+ log_line_current = 0;
+ else
+ free_log_line (log_line_current);
+ ln = log_lines + log_line_current;
+ if (len > STATIC_LENGTH)
+ {
+ ln->malloced_line = strdupdelim (start, end);
+ ln->content = ln->malloced_line;
+ }
+ else
+ {
+ memcpy (ln->static_line, start, len);
+ ln->static_line[len] = '\0';
+ ln->content = ln->static_line;
+ }
+ }
+ else
+ {
+ /* Append to the last line. If the line is malloc'ed, we just
+ call realloc and append the new string. If the line is
+ static, we have to check whether appending the new string
+ would make it exceed STATIC_LENGTH characters, and if so,
+ convert it to malloc(). */
+ struct log_ln *ln = log_lines + log_line_current;
+ if (ln->malloced_line)
+ {
+ /* Resize malloc'ed line and append. */
+ int old_len = strlen (ln->malloced_line);
+ ln->malloced_line = xrealloc (ln->malloced_line, old_len + len + 1);
+ memcpy (ln->malloced_line + old_len, start, len);
+ ln->malloced_line[old_len + len] = '\0';
+ /* might have changed due to realloc */
+ ln->content = ln->malloced_line;
+ }
+ else
+ {
+ int old_len = strlen (ln->static_line);
+ if (old_len + len > STATIC_LENGTH)
+ {
+ /* Allocate memory and concatenate the old and the new
+ contents. */
+ ln->malloced_line = xmalloc (old_len + len + 1);
+ memcpy (ln->malloced_line, ln->static_line,
+ old_len);
+ memcpy (ln->malloced_line + old_len, start, len);
+ ln->malloced_line[old_len + len] = '\0';
+ ln->content = ln->malloced_line;
+ }
+ else
+ {
+ /* Just append to the old, statically allocated
+ contents. */
+ memcpy (ln->static_line + old_len, start, len);
+ ln->static_line[old_len + len] = '\0';
+ ln->content = ln->static_line;
+ }
+ }
+ }
+ trailing_line = !(end[-1] == '\n');
+ if (!trailing_line)
+ ROT_ADVANCE (log_line_current);
+}