+ return ss_at_mblen (s, 0);
+}
+
+/* Advances S past the UTF-8 character at its beginning. Returns the Unicode
+ code point that was skipped (in the range 0 to 0x10ffff), or UINT32_MAX if S
+ was not modified because it was initially empty. */
+ucs4_t
+ss_get_mb (struct substring *s)
+{
+ if (s->length > 0)
+ {
+ ucs4_t uc;
+ int n;
+
+ n = u8_mbtouc (&uc, CHAR_CAST (const uint8_t *, s->string), s->length);
+ s->string += n;
+ s->length -= n;
+ return uc;
+ }
+ else
+ return UINT32_MAX;
+}
+
+/* Returns the character represented by the UTF-8 sequence starting OFS bytes
+ into S. The return value is either a Unicode code point in the range 0 to
+ 0x10ffff, or UINT32_MAX if OFS is past the last byte in S.
+
+ (Returns 0xfffd if OFS points into the middle, not the beginning, of a UTF-8
+ sequence.) */
+ucs4_t
+ss_at_mb (struct substring s, size_t ofs)
+{
+ if (s.length > ofs)
+ {
+ ucs4_t uc;
+ u8_mbtouc (&uc, CHAR_CAST (const uint8_t *, s.string + ofs),
+ s.length - ofs);
+ return uc;
+ }
+ else
+ return UINT32_MAX;
+}
+
+/* Returns the number of bytes represented by the UTF-8 sequence starting OFS
+ bytes into S. The return value is 0 if OFS is past the last byte in S,
+ otherwise between 1 and 4. */
+int
+ss_at_mblen (struct substring s, size_t ofs)
+{
+ if (s.length > ofs)
+ {
+ ucs4_t uc;
+ return u8_mbtouc (&uc, CHAR_CAST (const uint8_t *, s.string + ofs),
+ s.length - ofs);
+ }
+ else
+ return 0;
+}
+\f
+/* Initializes ST as an empty string. */
+void
+ds_init_empty (struct string *st)
+{
+ st->ss = ss_empty ();
+ st->capacity = 0;
+}
+
+/* Initializes ST with initial contents S. */
+void
+ds_init_string (struct string *st, const struct string *s)
+{
+ ds_init_substring (st, ds_ss (s));
+}
+
+/* Initializes ST with initial contents SS. */
+void
+ds_init_substring (struct string *st, struct substring ss)
+{
+ st->capacity = MAX (8, ss.length * 2);
+ st->ss.string = xmalloc (st->capacity + 1);
+ memcpy (st->ss.string, ss.string, ss.length);
+ st->ss.length = ss.length;
+}
+
+/* Initializes ST with initial contents S. */
+void
+ds_init_cstr (struct string *st, const char *s)
+{
+ ds_init_substring (st, ss_cstr (s));
+}
+
+/* Frees ST. */
+void
+ds_destroy (struct string *st)
+{
+ if (st != NULL)
+ {
+ ss_dealloc (&st->ss);
+ st->ss.string = NULL;
+ st->ss.length = 0;
+ st->capacity = 0;
+ }
+}
+
+/* Swaps the contents of strings A and B. */
+void
+ds_swap (struct string *a, struct string *b)
+{
+ struct string tmp = *a;
+ *a = *b;
+ *b = tmp;
+}
+
+/* Helper function for ds_register_pool. */
+static void
+free_string (void *st_)
+{
+ struct string *st = st_;
+ ds_destroy (st);
+}
+
+/* Arranges for ST to be destroyed automatically as part of
+ POOL. */
+void
+ds_register_pool (struct string *st, struct pool *pool)
+{
+ pool_register (pool, free_string, st);
+}
+
+/* Cancels the arrangement for ST to be destroyed automatically
+ as part of POOL. */
+void
+ds_unregister_pool (struct string *st, struct pool *pool)
+{
+ pool_unregister (pool, st);
+}
+
+/* Copies SRC into DST.
+ DST and SRC may be the same string. */
+void
+ds_assign_string (struct string *dst, const struct string *src)
+{
+ ds_assign_substring (dst, ds_ss (src));
+}
+
+/* Replaces DST by SS.
+ SS may be a substring of DST. */
+void
+ds_assign_substring (struct string *dst, struct substring ss)
+{
+ dst->ss.length = ss.length;
+ ds_extend (dst, ss.length);
+ memmove (dst->ss.string, ss.string, ss.length);
+}
+
+/* Replaces DST by null-terminated string SRC. SRC may overlap
+ with DST. */
+void
+ds_assign_cstr (struct string *dst, const char *src)
+{
+ ds_assign_substring (dst, ss_cstr (src));
+}
+
+/* Truncates ST to zero length. */
+void
+ds_clear (struct string *st)
+{
+ st->ss.length = 0;
+}
+
+/* Returns a substring that contains ST. */
+struct substring
+ds_ss (const struct string *st)
+{
+ return st->ss;
+}
+
+/* Returns a substring that contains CNT bytes from ST
+ starting at position START.
+
+ If START is greater than or equal to the length of ST, then
+ the substring will be the empty string. If START + CNT
+ exceeds the length of ST, then the substring will only be
+ ds_length(ST) - START bytes long. */
+struct substring
+ds_substr (const struct string *st, size_t start, size_t cnt)
+{
+ return ss_substr (ds_ss (st), start, cnt);
+}
+
+/* Returns a substring that contains the first CNT bytes in
+ ST. If CNT exceeds the length of ST, then the substring will
+ contain all of ST. */
+struct substring
+ds_head (const struct string *st, size_t cnt)
+{
+ return ss_head (ds_ss (st), cnt);
+}
+
+/* Returns a substring that contains the last CNT bytes in
+ ST. If CNT exceeds the length of ST, then the substring will
+ contain all of ST. */
+struct substring
+ds_tail (const struct string *st, size_t cnt)
+{
+ return ss_tail (ds_ss (st), cnt);
+}
+
+/* Ensures that ST can hold at least MIN_CAPACITY bytes plus a null
+ terminator. */
+void
+ds_extend (struct string *st, size_t min_capacity)
+{
+ if (min_capacity > st->capacity)
+ {
+ st->capacity *= 2;
+ if (st->capacity < min_capacity)
+ st->capacity = 2 * min_capacity;
+
+ st->ss.string = xrealloc (st->ss.string, st->capacity + 1);
+ }
+}
+
+/* Shrink ST to the minimum capacity need to contain its content. */
+void
+ds_shrink (struct string *st)
+{
+ if (st->capacity != st->ss.length)
+ {
+ st->capacity = st->ss.length;
+ st->ss.string = xrealloc (st->ss.string, st->capacity + 1);
+ }
+}
+
+/* Truncates ST to at most LENGTH bytes long. */
+void
+ds_truncate (struct string *st, size_t length)
+{
+ ss_truncate (&st->ss, length);
+}
+
+/* Removes trailing bytes in TRIM_SET from ST.
+ Returns number of bytes removed. */
+size_t
+ds_rtrim (struct string *st, struct substring trim_set)
+{
+ return ss_rtrim (&st->ss, trim_set);
+}
+
+/* Removes leading bytes in TRIM_SET from ST.
+ Returns number of bytes removed. */
+size_t
+ds_ltrim (struct string *st, struct substring trim_set)
+{
+ size_t cnt = ds_span (st, trim_set);
+ if (cnt > 0)
+ ds_assign_substring (st, ds_substr (st, cnt, SIZE_MAX));
+ return cnt;
+}
+
+/* Trims leading and trailing bytes in TRIM_SET from ST.
+ Returns number of bytes removed. */
+size_t
+ds_trim (struct string *st, struct substring trim_set)
+{
+ size_t cnt = ds_rtrim (st, trim_set);
+ return cnt + ds_ltrim (st, trim_set);
+}
+
+/* If the last byte in ST is C, removes it and returns true.
+ Otherwise, returns false without modifying ST. */
+bool
+ds_chomp (struct string *st, char c)
+{
+ return ss_chomp (&st->ss, c);
+}
+
+/* Divides ST into tokens separated by any of the DELIMITERS.
+ Each call replaces TOKEN by the next token in ST, or by an
+ empty string if no tokens remain. Returns true if a token was
+ obtained, false otherwise.
+
+ Before the first call, initialize *SAVE_IDX to 0. Do not
+ modify *SAVE_IDX between calls.
+
+ ST divides into exactly one more tokens than it contains
+ delimiters. That is, a delimiter at the start or end of ST or
+ a pair of adjacent delimiters yields an empty token, and the
+ empty string contains a single token. */
+bool
+ds_separate (const struct string *st, struct substring delimiters,
+ size_t *save_idx, struct substring *token)
+{
+ return ss_separate (ds_ss (st), delimiters, save_idx, token);
+}
+
+/* Divides ST into tokens separated by any of the DELIMITERS,
+ merging adjacent delimiters so that the empty string is never
+ produced as a token. Each call replaces TOKEN by the next
+ token in ST, or by an empty string if no tokens remain.
+ Returns true if a token was obtained, false otherwise.
+
+ Before the first call, initialize *SAVE_IDX to 0. Do not
+ modify *SAVE_IDX between calls. */
+bool
+ds_tokenize (const struct string *st, struct substring delimiters,
+ size_t *save_idx, struct substring *token)
+{
+ return ss_tokenize (ds_ss (st), delimiters, save_idx, token);
+}
+
+/* Pad ST on the right with copies of PAD until ST is at least
+ LENGTH bytes in size. If ST is initially LENGTH
+ bytes or longer, this is a no-op. */
+void
+ds_rpad (struct string *st, size_t length, char pad)
+{
+ if (length > st->ss.length)
+ ds_put_byte_multiple (st, pad, length - st->ss.length);
+}
+
+/* Sets the length of ST to exactly NEW_LENGTH,
+ either by truncating bytes from the end,
+ or by padding on the right with PAD. */
+void
+ds_set_length (struct string *st, size_t new_length, char pad)
+{
+ if (st->ss.length < new_length)
+ ds_rpad (st, new_length, pad);
+ else
+ st->ss.length = new_length;
+}
+
+/* Removes N bytes from ST starting at offset START. */
+void
+ds_remove (struct string *st, size_t start, size_t n)
+{
+ if (n > 0 && start < st->ss.length)
+ {
+ if (st->ss.length - start <= n)
+ {
+ /* All bytes at or beyond START are deleted. */
+ st->ss.length = start;
+ }
+ else
+ {
+ /* Some bytes remain and must be shifted into
+ position. */
+ memmove (st->ss.string + st->ss.length,
+ st->ss.string + st->ss.length + n,
+ st->ss.length - start - n);
+ st->ss.length -= n;
+ }
+ }
+ else
+ {
+ /* There are no bytes to delete or no bytes at or
+ beyond START, hence deletion is a no-op. */
+ }
+}
+
+/* Returns true if ST is empty, false otherwise. */
+bool
+ds_is_empty (const struct string *st)
+{
+ return ss_is_empty (st->ss);
+}
+
+/* Returns the length of ST. */
+size_t
+ds_length (const struct string *st)
+{
+ return ss_length (ds_ss (st));
+}
+
+/* Returns the string data inside ST. */
+char *
+ds_data (const struct string *st)
+{
+ return ss_data (ds_ss (st));
+}
+
+/* Returns a pointer to the null terminator ST.
+ This might not be an actual null byte unless ds_c_str() has
+ been called since the last modification to ST. */
+char *
+ds_end (const struct string *st)
+{
+ return ss_end (ds_ss (st));
+}
+
+/* Returns the byte in position IDX in ST, as a value in the
+ range of unsigned char. Returns EOF if IDX is out of the
+ range of indexes for ST. */
+int
+ds_at (const struct string *st, size_t idx)
+{
+ return ss_at (ds_ss (st), idx);
+}
+
+/* Returns the first byte in ST as a value in the range of
+ unsigned char. Returns EOF if ST is the empty string. */
+int
+ds_first (const struct string *st)
+{
+ return ss_first (ds_ss (st));
+}
+
+/* Returns the last byte in ST as a value in the range of
+ unsigned char. Returns EOF if ST is the empty string. */
+int
+ds_last (const struct string *st)
+{
+ return ss_last (ds_ss (st));
+}
+
+/* Returns the number of consecutive bytes at the beginning
+ of ST that are in SKIP_SET. */
+size_t
+ds_span (const struct string *st, struct substring skip_set)
+{
+ return ss_span (ds_ss (st), skip_set);
+}
+
+/* Returns the number of consecutive bytes at the beginning
+ of ST that are not in STOP_SET. */
+size_t
+ds_cspan (const struct string *st, struct substring stop_set)
+{
+ return ss_cspan (ds_ss (st), stop_set);
+}
+
+/* Returns the position of the first occurrence of byte C in
+ ST at or after position OFS, or SIZE_MAX if there is no such
+ occurrence. */
+size_t
+ds_find_byte (const struct string *st, char c)
+{
+ return ss_find_byte (ds_ss (st), c);
+}
+
+/* Compares A and B and returns a strcmp()-type comparison
+ result. */
+int
+ds_compare (const struct string *a, const struct string *b)
+{
+ return ss_compare (ds_ss (a), ds_ss (b));
+}
+
+/* Returns the position in ST that the byte at P occupies.
+ P must point within ST or one past its end. */
+size_t
+ds_pointer_to_position (const struct string *st, const char *p)
+{
+ return ss_pointer_to_position (ds_ss (st), p);
+}
+
+/* Allocates and returns a null-terminated string that contains
+ ST. */
+char *
+ds_xstrdup (const struct string *st)
+{
+ return ss_xstrdup (ds_ss (st));
+}
+
+/* Returns the allocation size of ST. */
+size_t
+ds_capacity (const struct string *st)
+{
+ return st->capacity;
+}
+
+/* Returns the value of ST as a null-terminated string. */
+char *
+ds_cstr (const struct string *st_)
+{
+ struct string *st = CONST_CAST (struct string *, st_);
+ if (st->ss.string == NULL)
+ ds_extend (st, 1);
+ st->ss.string[st->ss.length] = '\0';
+ return st->ss.string;
+}
+
+/* Returns the value of ST as a null-terminated string and then
+ reinitialized ST as an empty string. The caller must free the
+ returned string with free(). */
+char *
+ds_steal_cstr (struct string *st)
+{
+ char *s = ds_cstr (st);
+ ds_init_empty (st);
+ return s;
+}
+
+/* Reads bytes from STREAM and appends them to ST, stopping
+ after MAX_LENGTH bytes, after appending a newline, or
+ after an I/O error or end of file was encountered, whichever
+ comes first. Returns true if at least one byte was added
+ to ST, false if no bytes were read before an I/O error or
+ end of file (or if MAX_LENGTH was 0).
+
+ This function treats LF and CR LF sequences as new-line,
+ translating each of them to a single '\n' in ST. */
+bool
+ds_read_line (struct string *st, FILE *stream, size_t max_length)
+{
+ size_t length;
+
+ for (length = 0; length < max_length; length++)
+ {
+ int c = getc (stream);
+ switch (c)
+ {
+ case EOF:
+ return length > 0;
+
+ case '\n':
+ ds_put_byte (st, c);
+ return true;
+
+ case '\r':
+ c = getc (stream);
+ if (c == '\n')
+ {
+ /* CR followed by LF is special: translate to \n. */
+ ds_put_byte (st, '\n');
+ return true;
+ }
+ else
+ {
+ /* CR followed by anything else is just CR. */
+ ds_put_byte (st, '\r');
+ if (c == EOF)
+ return true;
+ ungetc (c, stream);
+ }
+ break;
+
+ default:
+ ds_put_byte (st, c);
+ }
+ }
+
+ return length > 0;
+}
+
+/* Removes a comment introduced by `#' from ST,
+ ignoring occurrences inside quoted strings. */
+static void
+remove_comment (struct string *st)
+{
+ char *cp;
+ int quote = 0;
+
+ for (cp = ds_data (st); cp < ds_end (st); cp++)
+ if (quote)
+ {
+ if (*cp == quote)
+ quote = 0;
+ else if (*cp == '\\')
+ cp++;
+ }
+ else if (*cp == '\'' || *cp == '"')
+ quote = *cp;
+ else if (*cp == '#')
+ {
+ ds_truncate (st, cp - ds_cstr (st));
+ break;
+ }
+}
+
+/* Reads a line from STREAM into ST, then preprocesses as follows:
+
+ - Splices lines terminated with `\'.
+
+ - Deletes comments introduced by `#' outside of single or double
+ quotes.
+
+ - Deletes trailing white space.
+
+ Returns true if a line was successfully read, false on
+ failure. If LINE_NUMBER is non-null, then *LINE_NUMBER is
+ incremented by the number of lines read. */
+bool
+ds_read_config_line (struct string *st, int *line_number, FILE *stream)
+{
+ ds_clear (st);
+ do
+ {
+ if (!ds_read_line (st, stream, SIZE_MAX))
+ return false;
+ (*line_number)++;
+ ds_rtrim (st, ss_cstr (CC_SPACES));
+ }
+ while (ds_chomp (st, '\\'));
+
+ remove_comment (st);
+ return true;
+}
+
+/* Attempts to read SIZE * CNT bytes from STREAM and append them
+ to ST.
+ Returns true if all the requested data was read, false otherwise. */
+bool
+ds_read_stream (struct string *st, size_t size, size_t cnt, FILE *stream)
+{
+ if (size != 0)
+ {
+ size_t try_bytes = xtimes (cnt, size);
+ if (size_in_bounds_p (xsum (ds_length (st), try_bytes)))
+ {
+ char *buffer = ds_put_uninit (st, try_bytes);
+ size_t got_bytes = fread (buffer, 1, try_bytes, stream);
+ ds_truncate (st, ds_length (st) - (try_bytes - got_bytes));
+ return got_bytes == try_bytes;
+ }
+ else
+ {
+ errno = ENOMEM;
+ return false;
+ }
+ }
+ else
+ return true;
+}
+
+/* Concatenates S onto ST. */
+void
+ds_put_cstr (struct string *st, const char *s)
+{
+ if (s != NULL)
+ ds_put_substring (st, ss_cstr (s));
+}
+
+/* Concatenates SS to ST. */
+void
+ds_put_substring (struct string *st, struct substring ss)
+{
+ memcpy (ds_put_uninit (st, ss_length (ss)), ss_data (ss), ss_length (ss));
+}
+
+/* Returns ds_end(ST) and THEN increases the length by INCR. */
+char *
+ds_put_uninit (struct string *st, size_t incr)
+{
+ char *end;
+ ds_extend (st, ds_length (st) + incr);
+ end = ds_end (st);
+ st->ss.length += incr;
+ return end;
+}
+
+/* Formats FORMAT as a printf string and appends the result to ST. */
+void
+ds_put_format (struct string *st, const char *format, ...)
+{
+ va_list args;
+
+ va_start (args, format);
+ ds_put_vformat (st, format, args);
+ va_end (args);
+}
+
+/* Formats FORMAT as a printf string and appends the result to ST. */
+void
+ds_put_vformat (struct string *st, const char *format, va_list args_)
+{
+ int avail, needed;
+ va_list args;
+
+ va_copy (args, args_);
+ avail = st->ss.string != NULL ? st->capacity - st->ss.length + 1 : 0;
+ needed = vsnprintf (st->ss.string + st->ss.length, avail, format, args);
+ va_end (args);
+
+ if (needed >= avail)
+ {
+ va_copy (args, args_);
+ vsprintf (ds_put_uninit (st, needed), format, args);
+ va_end (args);
+ }
+ else
+ {
+ /* Some old libc's returned -1 when the destination string
+ was too short. */
+ while (needed == -1)
+ {
+ ds_extend (st, (st->capacity + 1) * 2);
+ avail = st->capacity - st->ss.length + 1;
+
+ va_copy (args, args_);
+ needed = vsnprintf (ds_end (st), avail, format, args);
+ va_end (args);
+ }
+ st->ss.length += needed;
+ }
+}
+
+/* Appends byte CH to ST. */
+void
+ds_put_byte (struct string *st, int ch)
+{
+ ds_put_uninit (st, 1)[0] = ch;
+}
+
+/* Appends CNT copies of byte CH to ST. */
+void
+ds_put_byte_multiple (struct string *st, int ch, size_t cnt)
+{
+ memset (ds_put_uninit (st, cnt), ch, cnt);
+}
+
+
+/* If relocation has been enabled, replace ST,
+ with its relocated version */
+void
+ds_relocate (struct string *st)
+{
+ const char *orig = ds_cstr (st);
+ const char *rel = relocate (orig);
+
+ if ( orig != rel)
+ {
+ ds_clear (st);
+ ds_put_cstr (st, rel);
+ /* The documentation for relocate says that casting away const
+ and then freeing is appropriate ... */
+ free (CONST_CAST (char *, rel));
+ }
+}
+
+
+\f
+
+/* Operations on uint8_t "strings" */
+
+/* Copies buffer SRC, of SRC_SIZE bytes, to DST, of DST_SIZE bytes.
+ DST is truncated to DST_SIZE bytes or padded on the right with
+ copies of PAD as needed. */
+void
+u8_buf_copy_rpad (uint8_t *dst, size_t dst_size,
+ const uint8_t *src, size_t src_size,
+ char pad)
+{
+ if (src_size >= dst_size)
+ memmove (dst, src, dst_size);
+ else
+ {
+ memmove (dst, src, src_size);
+ memset (&dst[src_size], pad, dst_size - src_size);
+ }