Merge branch 'ordering'

2 files changed, 490 insertions, 453 deletions

diff --git a/src/sds.c b/src/sds.c
index b0e596e..57a2dc1 100644
--- a/src/sds.c
+++ b/src/sds.c
@@ -34,8 +34,8 @@
 
 #include "sds.h"
 
-int is_hex_digit(char c);
-int hex_digit_to_int(char c);
+
+/// Initialization
 
 /* Create a new sds string with the content specified by the 'init' pointer
  * and 'initlen'.
@@ -67,12 +67,6 @@ sds sdsnewlen(const void *init, size_t initlen) {
 	return (char*)sh->buf;
 }
 
-/* Create an empty (zero length) sds string. Even in this case the string
- * always has an implicit null term. */
-sds sdsempty(void) {
-	return sdsnewlen("", 0);
-}
-
 /* Create a new sds string starting from a null termined C string. */
 sds sdsnew(const char *init) {
 	size_t initlen = (init == NULL) ? 0 : strlen(init);
@@ -84,33 +78,60 @@ sds sdsdup(const sds s) {
 	return sdsnewlen(s, sdslen(s));
 }
 
-/* Free an sds string. No operation is performed if 's' is NULL. */
-void sdsfree(sds s) {
-	if (s == NULL) { return; }
-	free(sdsheader(s));
+/* Create an empty (zero length) sds string. Even in this case the string
+ * always has an implicit null term. */
+sds sdsempty(void) {
+	return sdsnewlen("", 0);
 }
 
-/* Set the sds string length to the length as obtained with strlen(), so
- * considering as content only up to the first null term character.
+/* Create an sds string from a long long value. It is much faster than:
  *
- * This function is useful when the sds string is hacked manually in some
- * way, like in the following example:
+ * sdscatprintf(sdsempty(), "%lld\n", value);
+ */
+sds sdsfromlonglong(long long value) {
+	char buf[32], *p;
+	unsigned long long v;
+
+	v = (unsigned long long)((value < 0) ? -value : value);
+	p = buf + 31; /* point to the last character */
+	do {
+		*p-- = '0' + (v%10);
+		v /= 10;
+	} while(v);
+	if (value < 0) { *p-- = '-'; }
+	p++;
+	return sdsnewlen(p, (size_t)(32 - (p - buf)));
+}
+
+
+/// Querying
+
+/* Compare two sds strings s1 and s2 with memcmp().
  *
- * s = sdsnew("foobar");
- * s[2] = '\0';
- * sdsupdatelen(s);
- * printf("%d\n", sdslen(s));
+ * Return value:
  *
- * The output will be "2", but if we comment out the call to sdsupdatelen()
- * the output will be "6" as the string was modified but the logical length
- * remains 6 bytes. */
-void sdsupdatelen(sds s) {
-	struct sdshdr *sh = sdsheader(s);
-	size_t reallen = strlen(s);
-	sh->free += (sh->len - reallen);
-	sh->len = reallen;
+ *     1 if s1 > s2.
+ *    -1 if s1 < s2.
+ *     0 if s1 and s2 are exactly the same binary string.
+ *
+ * If two strings share exactly the same prefix, but one of the two has
+ * additional characters, the longer string is considered to be greater than
+ * the smaller one. */
+int sdscmp(const sds s1, const sds s2) {
+	size_t l1, l2, minlen;
+	int cmp;
+
+	l1 = sdslen(s1);
+	l2 = sdslen(s2);
+	minlen = (l1 < l2) ? l1 : l2;
+	cmp = memcmp(s1, s2, minlen);
+	if (cmp == 0) { return (int)(l1 - l2); }
+	return cmp;
 }
 
+
+/// Modification
+
 /* Modify an sds string on-place to make it empty (zero length).
  * However all the existing buffer is not discarded but set as free space
  * so that next append operations will not require allocations up to the
@@ -122,94 +143,6 @@ void sdsclear(sds s) {
 	sh->buf[0] = '\0';
 }
 
-/* Enlarge the free space at the end of the sds string so that the caller
- * is sure that after calling this function can overwrite up to addlen
- * bytes after the end of the string, plus one more byte for nul term.
- * 
- * Note: this does not change the *length* of the sds string as returned
- * by sdslen(), but only the free buffer space we have. */
-sds sdsMakeRoomFor(sds s, size_t addlen) {
-	struct sdshdr *sh, *newsh;
-	size_t free = sdsavail(s);
-	size_t len, newlen;
-
-	if (free >= addlen) { return s; }
-	len = sdslen(s);
-	sh = sdsheader(s);
-	newlen = (len + addlen);
-	if (newlen < SDS_MAX_PREALLOC) {
-		newlen *= 2;
-	} else {
-		newlen += SDS_MAX_PREALLOC;
-	}
-	newsh = realloc(sh, sizeof(struct sdshdr) + newlen + 1);
-	if (newsh == NULL) { return NULL; }
-
-	newsh->free = newlen - len;
-	return newsh->buf;
-}
-
-/* Reallocate the sds string so that it has no free space at the end. The
- * contained string remains not altered, but next concatenation operations
- * will require a reallocation.
- *
- * After the call, the passed sds string is no longer valid and all the
- * references must be substituted with the new pointer returned by the call. */
-sds sdsRemoveFreeSpace(sds s) {
-	struct sdshdr *sh;
-
-	sh = sdsheader(s);
-	sh = realloc(sh, sizeof(struct sdshdr) + sh->len + 1);
-	sh->free = 0;
-	return sh->buf;
-}
-
-/* Return the total size of the allocation of the specifed sds string,
- * including:
- * 1) The sds header before the pointer.
- * 2) The string.
- * 3) The free buffer at the end if any.
- * 4) The implicit null term.
- */
-size_t sdsAllocSize(sds s) {
-	struct sdshdr *sh = sdsheader(s);
-
-	return sizeof(*sh) + sh->len + sh->free + 1;
-}
-
-/* Increment the sds length and decrements the left free space at the
- * end of the string according to 'incr'. Also set the null term
- * in the new end of the string.
- *
- * This function is used in order to fix the string length after the
- * user calls sdsMakeRoomFor(), writes something after the end of
- * the current string, and finally needs to set the new length.
- *
- * Note: it is possible to use a negative increment in order to
- * right-trim the string.
- *
- * Usage example:
- *
- * Using sdsIncrLen() and sdsMakeRoomFor() it is possible to mount the
- * following schema, to cat bytes coming from the kernel to the end of an
- * sds string without copying into an intermediate buffer:
- *
- * oldlen = sdslen(s);
- * s = sdsMakeRoomFor(s, BUFFER_SIZE);
- * nread = read(fd, s + oldlen, BUFFER_SIZE);
- * ... check for nread <= 0 and handle it ...
- * sdsIncrLen(s, nread);
- */
-void sdsIncrLen(sds s, size_t incr) {
-	struct sdshdr *sh = sdsheader(s);
-
-	assert(sh->free >= incr);
-	sh->len += incr;
-	sh->free -= incr;
-	assert(sh->free >= 0);
-	s[sh->len] = '\0';
-}
-
 /* Grow the sds to have the specified length. Bytes that were not part of
  * the original length of the sds will be set to zero.
  *
@@ -232,41 +165,6 @@ sds sdsgrowzero(sds s, size_t len) {
 	return s;
 }
 
-/* Append the specified binary-safe string pointed by 't' of 'len' bytes to the
- * end of the specified sds string 's'.
- *
- * After the call, the passed sds string is no longer valid and all the
- * references must be substituted with the new pointer returned by the call. */
-sds sdscatlen(sds s, const void *t, size_t len) {
-	struct sdshdr *sh;
-	size_t curlen = sdslen(s);
-
-	s = sdsMakeRoomFor(s, len);
-	if (s == NULL) { return NULL; }
-	sh = sdsheader(s);
-	memcpy(s + curlen, t, len);
-	sh->len = curlen + len;
-	sh->free = sh->free - len;
-	s[curlen + len] = '\0';
-	return s;
-}
-
-/* Append the specified null termianted C string to the sds string 's'.
- *
- * After the call, the passed sds string is no longer valid and all the
- * references must be substituted with the new pointer returned by the call. */
-sds sdscat(sds s, const char *t) {
-	return sdscatlen(s, t, strlen(t));
-}
-
-/* Append the specified sds 't' to the existing sds 's'.
- *
- * After the call, the modified sds string is no longer valid and all the
- * references must be substituted with the new pointer returned by the call. */
-sds sdscatsds(sds s, const sds t) {
-	return sdscatlen(s, t, sdslen(t));
-}
-
 /* Destructively modify the sds string 's' to hold the specified binary
  * safe string pointed by 't' of length 'len' bytes. */
 sds sdscpylen(sds s, const char *t, size_t len) {
@@ -292,85 +190,48 @@ sds sdscpy(sds s, const char *t) {
 	return sdscpylen(s, t, strlen(t));
 }
 
-/* Like sdscatpritf() but gets va_list instead of being variadic. */
-#pragma GCC diagnostic ignored "-Wformat-nonliteral"
-sds sdscatvprintf(sds s, const char *fmt, va_list ap) {
-	va_list cpy;
-	char *buf, *t;
-	size_t buflen = 16;
+/* Join an array of C strings using the specified separator (also a C string).
+ * Returns the result as an sds string. */
+sds sdsjoin(char **argv, int argc, char *sep, size_t seplen) {
+	sds join = sdsempty();
 
-	while(1) {
-		buf = malloc(buflen);
-		if (buf == NULL) { return NULL; }
-		buf[buflen - 2] = '\0';
-		va_copy(cpy, ap);
-		vsnprintf(buf, buflen, fmt, cpy);
-		if (buf[buflen - 2] != '\0') {
-			free(buf);
-			buflen *= 2;
-			continue;
-		}
-		break;
+	for (int j = 0; j < argc; j++) {
+		join = sdscat(join, argv[j]);
+		if (j != argc - 1) { join = sdscatlen(join, sep, seplen); }
 	}
-	t = sdscat(s, buf);
-	free(buf);
-	return t;
+	return join;
 }
-#pragma GCC diagnostic warning "-Wformat-nonliteral"
 
-/* Append to the sds string 's' a string obtained using printf-alike format
- * specifier.
- *
- * After the call, the modified sds string is no longer valid and all the
- * references must be substituted with the new pointer returned by the call.
- *
- * Example:
- *
- * s = sdsempty("Sum is: ");
- * s = sdscatprintf(s, "%d + %d = %d", a, b, a + b).
- *
- * Often you need to create a string from scratch with the printf-alike
- * format. When this is the need, just use sdsempty() as the target string:
- *
- * s = sdscatprintf(sdsempty(), "... your format ...", args);
- */
-sds sdscatprintf(sds s, const char *fmt, ...) {
-	va_list ap;
-	char *t;
-	va_start(ap, fmt);
-	t = sdscatvprintf(s, fmt, ap);
-	va_end(ap);
-	return t;
+/* Like sdsjoin, but joins an array of SDS strings. */
+sds sdsjoinsds(sds *argv, int argc, const char *sep, size_t seplen) {
+	sds join = sdsempty();
+
+	for (int j = 0; j < argc; j++) {
+		join = sdscatsds(join, argv[j]);
+		if (j != argc - 1) { join = sdscatlen(join, sep, seplen); }
+	}
+	return join;
 }
 
-/* Remove the part of the string from left and from right composed just of
- * contiguous characters found in 'cset', that is a null terminted C string.
- *
- * After the call, the modified sds string is no longer valid and all the
- * references must be substituted with the new pointer returned by the call.
- *
- * Example:
+/* Modify the string substituting all the occurrences of the set of
+ * characters specified in the 'from' string to the corresponding character
+ * in the 'to' array.
  *
- * s = sdsnew("AA...AA.a.aa.aHelloWorld     :::");
- * s = sdstrim(s, "A. :");
- * printf("%s\n", s);
+ * For instance: sdsmapchars(mystring, "ho", "01", 2)
+ * will have the effect of turning the string "hello" into "0ell1".
  *
- * Output will be just "Hello World".
- */
-void sdstrim(sds s, const char *cset) {
-	struct sdshdr *sh = sdsheader(s);
-	char *start, *end, *sp, *ep;
-	size_t len;
-
-	sp = start = s;
-	ep = end = s + sdslen(s) - 1;
-	while(sp <= end && strchr(cset, *sp)) { sp++; }
-	while(ep > start && strchr(cset, *ep)) { ep--; }
-	len = (size_t)((sp > ep) ? 0 : ((ep - sp) + 1));
-	if (sh->buf != sp) { memmove(sh->buf, sp, len); }
-	sh->buf[len] = '\0';
-	sh->free = sh->free + (sh->len - len);
-	sh->len = len;
+ * The function returns the sds string pointer, that is always the same
+ * as the input pointer since no resize is needed. */
+sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen) {
+	for (size_t j = 0; j < sdslen(s); j++) {
+		for (size_t i = 0; i < setlen; i++) {
+			if (s[j] == from[i]) {
+				s[j] = to[i];
+				break;
+			}
+		}
+	}
+	return s;
 }
 
 /* Turn the string into a smaller (or equal) string containing only the
@@ -433,182 +294,55 @@ void sdstoupper(sds s) {
 	}
 }
 
-/* Compare two sds strings s1 and s2 with memcmp().
- *
- * Return value:
- *
- *     1 if s1 > s2.
- *    -1 if s1 < s2.
- *     0 if s1 and s2 are exactly the same binary string.
+/* Remove the part of the string from left and from right composed just of
+ * contiguous characters found in 'cset', that is a null terminted C string.
  *
- * If two strings share exactly the same prefix, but one of the two has
- * additional characters, the longer string is considered to be greater than
- * the smaller one. */
-int sdscmp(const sds s1, const sds s2) {
-	size_t l1, l2, minlen;
-	int cmp;
-
-	l1 = sdslen(s1);
-	l2 = sdslen(s2);
-	minlen = (l1 < l2) ? l1 : l2;
-	cmp = memcmp(s1, s2, minlen);
-	if (cmp == 0) { return (int)(l1 - l2); }
-	return cmp;
-}
-
-/* Split 's' with separator in 'sep'. An array
- * of sds strings is returned. *count will be set
- * by reference to the number of tokens returned.
+ * After the call, the modified sds string is no longer valid and all the
+ * references must be substituted with the new pointer returned by the call.
  *
- * On out of memory, zero length string, zero length
- * separator, NULL is returned.
+ * Example:
  *
- * Note that 'sep' is able to split a string using
- * a multi-character separator. For example
- * sdssplit("foo_-_bar", "_-_"); will return two
- * elements "foo" and "bar".
+ * s = sdsnew("AA...AA.a.aa.aHelloWorld     :::");
+ * s = sdstrim(s, "A. :");
+ * printf("%s\n", s);
  *
- * This version of the function is binary-safe but
- * requires length arguments. sdssplit() is just the
- * same function but for zero-terminated strings.
+ * Output will be just "Hello World".
  */
-sds *sdssplitlen(const char *s, size_t len, const char *sep, size_t seplen, size_t *count) {
-	size_t elements = 0, slots = 5, start = 0;
-	sds *tokens;
-
-	if (seplen < 1) { return NULL; }
-
-	tokens = malloc(sizeof(sds)*slots);
-	if (tokens == NULL) { return NULL; }
-
-	if (len == 0) {
-		*count = 0;
-		return tokens;
-	}
-	for (size_t j = 0; j < (len - (seplen - 1)); j++) {
-		/* make sure there is room for the next element and the final one */
-		if (slots < elements + 2) {
-			sds *newtokens;
-
-			slots *= 2;
-			newtokens = realloc(tokens, sizeof(sds) * slots);
-			if (newtokens == NULL) { goto cleanup; }
-			tokens = newtokens;
-		}
-		/* search the separator */
-		if ((seplen == 1 && *(s + j) == sep[0]) || (memcmp(s + j, sep, seplen) == 0)) {
-			tokens[elements] = sdsnewlen(s + start, (size_t)(j - start));
-			if (tokens[elements] == NULL) { goto cleanup; }
-			elements++;
-			start = j + seplen;
-			j = j + seplen - 1; /* skip the separator */
-		}
-	}
-	/* Add the final element. We are sure there is room in the tokens array. */
-	tokens[elements] = sdsnewlen(s + start, (size_t)(len - start));
-	if (tokens[elements] == NULL) { goto cleanup; }
-	elements++;
-	*count = elements;
-	return tokens;
-
-cleanup:
-	{
-		for (size_t i = 0; i < elements; i++) sdsfree(tokens[i]);
-		free(tokens);
-		*count = 0;
-		return NULL;
-	}
-}
+void sdstrim(sds s, const char *cset) {
+	struct sdshdr *sh = sdsheader(s);
+	char *start, *end, *sp, *ep;
+	size_t len;
 
-/* Free the result returned by sdssplitlen(), or do nothing if 'tokens' is NULL. */
-void sdsfreesplitres(sds *tokens, size_t count) {
-	if (!tokens) { return; }
-	while(count--) {
-		sdsfree(tokens[count]);
-	}
-	free(tokens);
+	sp = start = s;
+	ep = end = s + sdslen(s) - 1;
+	while(sp <= end && strchr(cset, *sp)) { sp++; }
+	while(ep > start && strchr(cset, *ep)) { ep--; }
+	len = (size_t)((sp > ep) ? 0 : ((ep - sp) + 1));
+	if (sh->buf != sp) { memmove(sh->buf, sp, len); }
+	sh->buf[len] = '\0';
+	sh->free = sh->free + (sh->len - len);
+	sh->len = len;
 }
 
-/* Create an sds string from a long long value. It is much faster than:
+/* Set the sds string length to the length as obtained with strlen(), so
+ * considering as content only up to the first null term character.
  *
- * sdscatprintf(sdsempty(), "%lld\n", value);
- */
-sds sdsfromlonglong(long long value) {
-	char buf[32], *p;
-	unsigned long long v;
-
-	v = (unsigned long long)((value < 0) ? -value : value);
-	p = buf + 31; /* point to the last character */
-	do {
-		*p-- = '0' + (v%10);
-		v /= 10;
-	} while(v);
-	if (value < 0) { *p-- = '-'; }
-	p++;
-	return sdsnewlen(p, (size_t)(32 - (p - buf)));
-}
-
-/* Append to the sds string "s" an escaped string representation where
- * all the non-printable characters (tested with isprint()) are turned into
- * escapes in the form "\n\r\a...." or "\x<hex-number>".
+ * This function is useful when the sds string is hacked manually in some
+ * way, like in the following example:
  *
- * After the call, the modified sds string is no longer valid and all the
- * references must be substituted with the new pointer returned by the call. */
-sds sdscatrepr(sds s, const char *p, size_t len) {
-	s = sdscatlen(s, "\"", 1);
-	while(len--) {
-		switch(*p) {
-		case '\\':
-		case '"':
-			s = sdscatprintf(s, "\\%c", *p);
-			break;
-		case '\n': s = sdscatlen(s, "\\n", 2); break;
-		case '\r': s = sdscatlen(s, "\\r", 2); break;
-		case '\t': s = sdscatlen(s, "\\t", 2); break;
-		case '\a': s = sdscatlen(s, "\\a", 2); break;
-		case '\b': s = sdscatlen(s, "\\b", 2); break;
-		default:
-			if (isprint(*p)) {
-				s = sdscatprintf(s, "%c", *p);
-			} else {
-				s = sdscatprintf(s, "\\x%02x", (unsigned char)*p);
-				break;
-			}
-		}
-		p++;
-	}
-	return sdscatlen(s, "\"", 1);
-}
-
-/* Helper function for sdssplitargs() that returns non zero if 'c'
- * is a valid hex digit. */
-int is_hex_digit(char c) {
-	return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') ||
-	       (c >= 'A' && c <= 'F');
-}
-
-/* Helper function for sdssplitargs() that converts a hex digit into an
- * integer from 0 to 15 */
-int hex_digit_to_int(char c) {
-	switch(c) {
-	case '0': return 0;
-	case '1': return 1;
-	case '2': return 2;
-	case '3': return 3;
-	case '4': return 4;
-	case '5': return 5;
-	case '6': return 6;
-	case '7': return 7;
-	case '8': return 8;
-	case '9': return 9;
-	case 'a': case 'A': return 10;
-	case 'b': case 'B': return 11;
-	case 'c': case 'C': return 12;
-	case 'd': case 'D': return 13;
-	case 'e': case 'E': return 14;
-	case 'f': case 'F': return 15;
-	default: return 0;
-	}
+ * s = sdsnew("foobar");
+ * s[2] = '\0';
+ * sdsupdatelen(s);
+ * printf("%d\n", sdslen(s));
+ *
+ * The output will be "2", but if we comment out the call to sdsupdatelen()
+ * the output will be "6" as the string was modified but the logical length
+ * remains 6 bytes. */
+void sdsupdatelen(sds s) {
+	struct sdshdr *sh = sdsheader(s);
+	size_t reallen = strlen(s);
+	sh->free += (sh->len - reallen);
+	sh->len = reallen;
 }
 
 /* Split a line into arguments, where every argument can be in the
@@ -741,46 +475,330 @@ err:
 	return NULL;
 }
 
-/* Modify the string substituting all the occurrences of the set of
- * characters specified in the 'from' string to the corresponding character
- * in the 'to' array.
+/* Split 's' with separator in 'sep'. An array
+ * of sds strings is returned. *count will be set
+ * by reference to the number of tokens returned.
  *
- * For instance: sdsmapchars(mystring, "ho", "01", 2)
- * will have the effect of turning the string "hello" into "0ell1".
+ * On out of memory, zero length string, zero length
+ * separator, NULL is returned.
  *
- * The function returns the sds string pointer, that is always the same
- * as the input pointer since no resize is needed. */
-sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen) {
-	for (size_t j = 0; j < sdslen(s); j++) {
-		for (size_t i = 0; i < setlen; i++) {
-			if (s[j] == from[i]) {
-				s[j] = to[i];
+ * Note that 'sep' is able to split a string using
+ * a multi-character separator. For example
+ * sdssplit("foo_-_bar", "_-_"); will return two
+ * elements "foo" and "bar".
+ *
+ * This version of the function is binary-safe but
+ * requires length arguments. sdssplit() is just the
+ * same function but for zero-terminated strings.
+ */
+sds *sdssplitlen(const char *s, size_t len, const char *sep, size_t seplen, size_t *count) {
+	size_t elements = 0, slots = 5, start = 0;
+	sds *tokens;
+
+	if (seplen < 1) { return NULL; }
+
+	tokens = malloc(sizeof(sds)*slots);
+	if (tokens == NULL) { return NULL; }
+
+	if (len == 0) {
+		*count = 0;
+		return tokens;
+	}
+	for (size_t j = 0; j < (len - (seplen - 1)); j++) {
+		/* make sure there is room for the next element and the final one */
+		if (slots < elements + 2) {
+			sds *newtokens;
+
+			slots *= 2;
+			newtokens = realloc(tokens, sizeof(sds) * slots);
+			if (newtokens == NULL) { goto cleanup; }
+			tokens = newtokens;
+		}
+		/* search the separator */
+		if ((seplen == 1 && *(s + j) == sep[0]) || (memcmp(s + j, sep, seplen) == 0)) {
+			tokens[elements] = sdsnewlen(s + start, (size_t)(j - start));
+			if (tokens[elements] == NULL) { goto cleanup; }
+			elements++;
+			start = j + seplen;
+			j = j + seplen - 1; /* skip the separator */
+		}
+	}
+	/* Add the final element. We are sure there is room in the tokens array. */
+	tokens[elements] = sdsnewlen(s + start, (size_t)(len - start));
+	if (tokens[elements] == NULL) { goto cleanup; }
+	elements++;
+	*count = elements;
+	return tokens;
+
+cleanup:
+	{
+		for (size_t i = 0; i < elements; i++) sdsfree(tokens[i]);
+		free(tokens);
+		*count = 0;
+		return NULL;
+	}
+}
+
+// Concatenation
+
+/* Append the specified null termianted C string to the sds string 's'.
+ *
+ * After the call, the passed sds string is no longer valid and all the
+ * references must be substituted with the new pointer returned by the call. */
+sds sdscat(sds s, const char *t) {
+	return sdscatlen(s, t, strlen(t));
+}
+
+/* Append the specified sds 't' to the existing sds 's'.
+ *
+ * After the call, the modified sds string is no longer valid and all the
+ * references must be substituted with the new pointer returned by the call. */
+sds sdscatsds(sds s, const sds t) {
+	return sdscatlen(s, t, sdslen(t));
+}
+
+/* Append the specified binary-safe string pointed by 't' of 'len' bytes to the
+ * end of the specified sds string 's'.
+ *
+ * After the call, the passed sds string is no longer valid and all the
+ * references must be substituted with the new pointer returned by the call. */
+sds sdscatlen(sds s, const void *t, size_t len) {
+	struct sdshdr *sh;
+	size_t curlen = sdslen(s);
+
+	s = sdsMakeRoomFor(s, len);
+	if (s == NULL) { return NULL; }
+	sh = sdsheader(s);
+	memcpy(s + curlen, t, len);
+	sh->len = curlen + len;
+	sh->free = sh->free - len;
+	s[curlen + len] = '\0';
+	return s;
+}
+
+/* Append to the sds string "s" an escaped string representation where
+ * all the non-printable characters (tested with isprint()) are turned into
+ * escapes in the form "\n\r\a...." or "\x<hex-number>".
+ *
+ * After the call, the modified sds string is no longer valid and all the
+ * references must be substituted with the new pointer returned by the call. */
+sds sdscatrepr(sds s, const char *p, size_t len) {
+	s = sdscatlen(s, "\"", 1);
+	while(len--) {
+		switch(*p) {
+		case '\\':
+		case '"':
+			s = sdscatprintf(s, "\\%c", *p);
+			break;
+		case '\n': s = sdscatlen(s, "\\n", 2); break;
+		case '\r': s = sdscatlen(s, "\\r", 2); break;
+		case '\t': s = sdscatlen(s, "\\t", 2); break;
+		case '\a': s = sdscatlen(s, "\\a", 2); break;
+		case '\b': s = sdscatlen(s, "\\b", 2); break;
+		default:
+			if (isprint(*p)) {
+				s = sdscatprintf(s, "%c", *p);
+			} else {
+				s = sdscatprintf(s, "\\x%02x", (unsigned char)*p);
 				break;
 			}
 		}
+		p++;
 	}
-	return s;
+	return sdscatlen(s, "\"", 1);
 }
 
-/* Join an array of C strings using the specified separator (also a C string).
- * Returns the result as an sds string. */
-sds sdsjoin(char **argv, int argc, char *sep, size_t seplen) {
-	sds join = sdsempty();
+/* Like sdscatpritf() but gets va_list instead of being variadic. */
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+sds sdscatvprintf(sds s, const char *fmt, va_list ap) {
+	va_list cpy;
+	char *buf, *t;
+	size_t buflen = 16;
 
-	for (int j = 0; j < argc; j++) {
-		join = sdscat(join, argv[j]);
-		if (j != argc - 1) { join = sdscatlen(join, sep, seplen); }
+	while(1) {
+		buf = malloc(buflen);
+		if (buf == NULL) { return NULL; }
+		buf[buflen - 2] = '\0';
+		va_copy(cpy, ap);
+		vsnprintf(buf, buflen, fmt, cpy);
+		if (buf[buflen - 2] != '\0') {
+			free(buf);
+			buflen *= 2;
+			continue;
+		}
+		break;
 	}
-	return join;
+	t = sdscat(s, buf);
+	free(buf);
+	return t;
 }
+#pragma GCC diagnostic warning "-Wformat-nonliteral"
 
-/* Like sdsjoin, but joins an array of SDS strings. */
-sds sdsjoinsds(sds *argv, int argc, const char *sep, size_t seplen) {
-	sds join = sdsempty();
+/* Append to the sds string 's' a string obtained using printf-alike format
+ * specifier.
+ *
+ * After the call, the modified sds string is no longer valid and all the
+ * references must be substituted with the new pointer returned by the call.
+ *
+ * Example:
+ *
+ * s = sdsempty("Sum is: ");
+ * s = sdscatprintf(s, "%d + %d = %d", a, b, a + b).
+ *
+ * Often you need to create a string from scratch with the printf-alike
+ * format. When this is the need, just use sdsempty() as the target string:
+ *
+ * s = sdscatprintf(sdsempty(), "... your format ...", args);
+ */
+sds sdscatprintf(sds s, const char *fmt, ...) {
+	va_list ap;
+	char *t;
+	va_start(ap, fmt);
+	t = sdscatvprintf(s, fmt, ap);
+	va_end(ap);
+	return t;
+}
 
-	for (int j = 0; j < argc; j++) {
-		join = sdscatsds(join, argv[j]);
-		if (j != argc - 1) { join = sdscatlen(join, sep, seplen); }
+
+/// Freeing
+
+/* Free an sds string. No operation is performed if 's' is NULL. */
+void sdsfree(sds s) {
+	if (s == NULL) { return; }
+	free(sdsheader(s));
+}
+
+/* Free the result returned by sdssplitlen(), or do nothing if 'tokens' is NULL. */
+void sdsfreesplitres(sds *tokens, size_t count) {
+	if (!tokens) { return; }
+	while(count--) {
+		sdsfree(tokens[count]);
 	}
-	return join;
+	free(tokens);
+}
+
+
+// Low-level functions
+
+/* Return the total size of the allocation of the specifed sds string,
+ * including:
+ * 1) The sds header before the pointer.
+ * 2) The string.
+ * 3) The free buffer at the end if any.
+ * 4) The implicit null term.
+ */
+size_t sdsAllocSize(sds s) {
+	struct sdshdr *sh = sdsheader(s);
+
+	return sizeof(*sh) + sh->len + sh->free + 1;
+}
+
+/* Increment the sds length and decrements the left free space at the
+ * end of the string according to 'incr'. Also set the null term
+ * in the new end of the string.
+ *
+ * This function is used in order to fix the string length after the
+ * user calls sdsMakeRoomFor(), writes something after the end of
+ * the current string, and finally needs to set the new length.
+ *
+ * Note: it is possible to use a negative increment in order to
+ * right-trim the string.
+ *
+ * Usage example:
+ *
+ * Using sdsIncrLen() and sdsMakeRoomFor() it is possible to mount the
+ * following schema, to cat bytes coming from the kernel to the end of an
+ * sds string without copying into an intermediate buffer:
+ *
+ * oldlen = sdslen(s);
+ * s = sdsMakeRoomFor(s, BUFFER_SIZE);
+ * nread = read(fd, s + oldlen, BUFFER_SIZE);
+ * ... check for nread <= 0 and handle it ...
+ * sdsIncrLen(s, nread);
+ */
+void sdsIncrLen(sds s, size_t incr) {
+	struct sdshdr *sh = sdsheader(s);
+
+	assert(sh->free >= incr);
+	sh->len += incr;
+	sh->free -= incr;
+	assert(sh->free >= 0);
+	s[sh->len] = '\0';
 }
+
+/* Enlarge the free space at the end of the sds string so that the caller
+ * is sure that after calling this function can overwrite up to addlen
+ * bytes after the end of the string, plus one more byte for nul term.
+ * 
+ * Note: this does not change the *length* of the sds string as returned
+ * by sdslen(), but only the free buffer space we have. */
+sds sdsMakeRoomFor(sds s, size_t addlen) {
+	struct sdshdr *sh, *newsh;
+	size_t free = sdsavail(s);
+	size_t len, newlen;
+
+	if (free >= addlen) { return s; }
+	len = sdslen(s);
+	sh = sdsheader(s);
+	newlen = (len + addlen);
+	if (newlen < SDS_MAX_PREALLOC) {
+		newlen *= 2;
+	} else {
+		newlen += SDS_MAX_PREALLOC;
+	}
+	newsh = realloc(sh, sizeof(struct sdshdr) + newlen + 1);
+	if (newsh == NULL) { return NULL; }
+
+	newsh->free = newlen - len;
+	return newsh->buf;
+}
+
+/* Reallocate the sds string so that it has no free space at the end. The
+ * contained string remains not altered, but next concatenation operations
+ * will require a reallocation.
+ *
+ * After the call, the passed sds string is no longer valid and all the
+ * references must be substituted with the new pointer returned by the call. */
+sds sdsRemoveFreeSpace(sds s) {
+	struct sdshdr *sh;
+
+	sh = sdsheader(s);
+	sh = realloc(sh, sizeof(struct sdshdr) + sh->len + 1);
+	sh->free = 0;
+	return sh->buf;
+}
+
+
+/// Low-level helper functions
+
+/* Helper function for sdssplitargs() that returns non zero if 'c'
+ * is a valid hex digit. */
+int is_hex_digit(char c) {
+	return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') ||
+	       (c >= 'A' && c <= 'F');
+}
+
+/* Helper function for sdssplitargs() that converts a hex digit into an
+ * integer from 0 to 15 */
+int hex_digit_to_int(char c) {
+	switch(c) {
+	case '0': return 0;
+	case '1': return 1;
+	case '2': return 2;
+	case '3': return 3;
+	case '4': return 4;
+	case '5': return 5;
+	case '6': return 6;
+	case '7': return 7;
+	case '8': return 8;
+	case '9': return 9;
+	case 'a': case 'A': return 10;
+	case 'b': case 'B': return 11;
+	case 'c': case 'C': return 12;
+	case 'd': case 'D': return 13;
+	case 'e': case 'E': return 14;
+	case 'f': case 'F': return 15;
+	default: return 0;
+	}
+}
+
diff --git a/src/sds.h b/src/sds.h
index 3354096..501ac53 100644
--- a/src/sds.h
+++ b/src/sds.h
@@ -56,48 +56,67 @@ static inline size_t sdsavail(const sds s) {
 	return sdsheader(s)->free;
 }
 
-sds sdsnewlen(const void *init, size_t initlen);
-sds sdsnew(const char *init);
-sds sdsempty(void);
-size_t sdslen(const sds s);
-sds sdsdup(const sds s);
-void sdsfree(sds s);
+/**
+ * User API function prototypes
+ */
+
+/// Initialization
+sds    sdsnewlen(const void *init, size_t initlen);
+sds    sdsnew(const char *init);
+sds    sdsdup(const sds s);
+sds    sdsempty(void);
+sds    sdsfromlonglong(long long value);
+
+
+/// Querying
 size_t sdsavail(const sds s);
-sds sdsgrowzero(sds s, size_t len);
-sds sdscatlen(sds s, const void *t, size_t len);
-sds sdscat(sds s, const char *t);
-sds sdscatsds(sds s, const sds t);
-sds sdscpylen(sds s, const char *t, size_t len);
-sds sdscpy(sds s, const char *t);
-
-sds sdscatvprintf(sds s, const char *fmt, va_list ap);
+size_t sdslen(const sds s);
+int    sdscmp(const sds s1, const sds s2);
+
+
+/// Modification
+void   sdsclear(sds s);
+sds    sdsgrowzero(sds s, size_t len);
+sds    sdscpylen(sds s, const char *t, size_t len);
+sds    sdscpy(sds s, const char *t);
+sds    sdsjoin(char **argv, int argc, char *sep, size_t seplen);
+sds    sdsjoinsds(sds *argv, int argc, const char *sep, size_t seplen);
+sds    sdsmapchars(sds s, const char *from, const char *to, size_t setlen);
+void   sdsrange(sds s, ptrdiff_t start, ptrdiff_t end);
+void   sdstolower(sds s);
+void   sdstoupper(sds s);
+void   sdstrim(sds s, const char *cset);
+void   sdsupdatelen(sds s);
+sds   *sdssplitargs(const char *line, int *argc);
+sds   *sdssplitlen(const char *s, size_t len, const char *sep, size_t seplen, size_t *count);
+
+// Concatenation
+sds    sdscat(sds s, const char *t);
+sds    sdscatsds(sds s, const sds t);
+sds    sdscatlen(sds s, const void *t, size_t len);
+sds    sdscatrepr(sds s, const char *p, size_t len);
+sds    sdscatvprintf(sds s, const char *fmt, va_list ap);
 #ifdef __GNUC__
-sds sdscatprintf(sds s, const char *fmt, ...)
-    __attribute__((format(printf, 2, 3)));
+sds    sdscatprintf(sds s, const char *fmt, ...)
+            __attribute__((format(printf, 2, 3)));
 #else
-sds sdscatprintf(sds s, const char *fmt, ...);
+sds    sdscatprintf(sds s, const char *fmt, ...);
 #endif
 
-void sdstrim(sds s, const char *cset);
-void sdsrange(sds s, ptrdiff_t start, ptrdiff_t end);
-void sdsupdatelen(sds s);
-void sdsclear(sds s);
-int sdscmp(const sds s1, const sds s2);
-sds *sdssplitlen(const char *s, size_t len, const char *sep, size_t seplen, size_t *count);
-void sdsfreesplitres(sds *tokens, size_t count);
-void sdstolower(sds s);
-void sdstoupper(sds s);
-sds sdsfromlonglong(long long value);
-sds sdscatrepr(sds s, const char *p, size_t len);
-sds *sdssplitargs(const char *line, int *argc);
-sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen);
-sds sdsjoin(char **argv, int argc, char *sep, size_t seplen);
-sds sdsjoinsds(sds *argv, int argc, const char *sep, size_t seplen);
-
-/* Low level functions exposed to the user API */
-sds sdsMakeRoomFor(sds s, size_t addlen);
-void sdsIncrLen(sds s, size_t incr);
-sds sdsRemoveFreeSpace(sds s);
+
+/// Freeing
+void   sdsfree(sds s);
+void   sdsfreesplitres(sds *tokens, size_t count);
+
+
+/// Low-level functions
 size_t sdsAllocSize(sds s);
+void   sdsIncrLen(sds s, size_t incr);
+sds    sdsMakeRoomFor(sds s, size_t addlen);
+sds    sdsRemoveFreeSpace(sds s);
+
+/// Low-level helper functions
+int    is_hex_digit(char c);
+int    hex_digit_to_int(char c);
 
 #endif