include/common/ist.h - haproxy - Gitiles

 /*
  * include/common/ist.h
  * Very simple indirect string manipulation functions.
  *
  * Copyright (C) 2014-2017 Willy Tarreau - w@1wt.eu
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
  * "Software"), to deal in the Software without restriction, including
  * without limitation the rights to use, copy, modify, merge, publish,
  * distribute, sublicense, and/or sell copies of the Software, and to
  * permit persons to whom the Software is furnished to do so, subject to
  * the following conditions:
  *
  * The above copyright notice and this permission notice shall be
  * included in all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  * OTHER DEALINGS IN THE SOFTWARE.
  */

 #ifndef _COMMON_IST_H
 #define _COMMON_IST_H

 #include <string.h>

 #include <common/config.h>

 /* This string definition will most often be used to represent a read-only
  * string returned from a function, based on the starting point and its length
  * in bytes. No storage is provided, only a pointer and a length. The types
  * here are important as we only want to have 2 native machine words there so
  * that on modern architectures the compiler is capable of efficiently
  * returning a register pair without having to allocate stack room from the
  * caller. This is done with -freg-struct which is often enabled by default.
  */
 struct ist {
 	char  *ptr;
 	size_t len;
 };

 /* makes a constant ist from a constant string, for use in array declarations */
 #define IST(str) { .ptr = str "", .len = (sizeof str "") - 1 }

 /* makes an ist from a regular zero terminated string. Null has length 0.
  * Constants are detected and replaced with constant initializers. Other values
  * are measured by hand without strlen() as it's much cheaper and inlinable on
  * small strings. The construct is complex because we must never call
  * __builtin_strlen() with an expression otherwise it involves a real
  * measurement.
  */
 #if __GNUC__ >= 4
 // gcc >= 4 detects constant propagation of str through __x and resolves the
 // length of constant strings easily.
 #define ist(str) ({                                                    \
 	char *__x = (void *)(str);                                     \
 	(struct ist){                                                  \
 		.ptr = __x,                                            \
 		.len = __builtin_constant_p(str) ?                     \
 			((void *)str == (void *)0) ? 0 :               \
 			__builtin_strlen(__x) :                        \
 			({                                             \
 				size_t __l = 0;                        \
 				if (__x) for (__l--; __x[++__l]; ) ;   \
 				__l;                                   \
 			})                                             \
 	};                                                             \
 })
 #else
 // gcc < 4 can't do this, and the side effect is a warning each time a NULL is
 // passed to ist() due to the check on __builtin_strlen(). It doesn't have the
 // ability to know that this code is never called.
 #define ist(str) ({                                                    \
 	char *__x = (void *)(str);                                     \
 	(struct ist){                                                  \
 		.ptr = __x,                                            \
 		.len = __builtin_constant_p(str) ?                     \
 			((void *)str == (void *)0) ? 0 :               \
 			__builtin_strlen(str) :                        \
 			({                                             \
 				size_t __l = 0;                        \
 				if (__x) for (__l--; __x[++__l]; ) ;   \
 				__l;                                   \
 			})                                             \
 	};                                                             \
 })
 #endif

 /* makes an ist struct from a string and a length */
 static inline struct ist ist2(const void *ptr, size_t len)
 {
 	return (struct ist){ .ptr = (char *)ptr, .len = len };
 }

 /* returns the length of the string */
 static inline size_t istlen(const struct ist ist)
 {
 	return ist.len;
 }

 /* skips to next character in the string, always stops at the end */
 static inline struct ist istnext(const struct ist ist)
 {
 	struct ist ret = ist;

 	if (ret.len) {
 		ret.len--;
 		ret.ptr++;
 	}
 	return ret;
 }

 /* copies the contents from string <ist> to buffer <buf> and adds a trailing
  * zero. The caller must ensure <buf> is large enough.
  */
 static inline struct ist istpad(void *buf, const struct ist ist)
 {
 	struct ist ret = { .ptr = buf, .len = ist.len };

 	for (ret.len = 0; ret.len < ist.len; ret.len++)
 		ret.ptr[ret.len] = ist.ptr[ret.len];

 	ret.ptr[ret.len] = 0;
 	return ret;
 }

 /* trims string <ist> to no more than <size> characters. The string is
  * returned.
  */
 static inline struct ist isttrim(const struct ist ist, size_t size)
 {
 	struct ist ret = ist;

 	if (ret.len > size)
 		ret.len = size;
 	return ret;
 }

 /* trims string <ist> to no more than <size>-1 characters and ensures that a
  * zero is placed after <ist.len> (possibly reduced by one) and before <size>,
  * unless <size> is already zero. The string is returned. This is mostly aimed
  * at building printable strings that need to be zero-terminated.
  */
 static inline struct ist istzero(const struct ist ist, size_t size)
 {
 	struct ist ret = ist;

 	if (!size)
 		ret.len = 0;
 	else {
 		if (ret.len > size - 1)
 			ret.len = size - 1;
 		ret.ptr[ret.len] = 0;
 	}
 	return ret;
 }

 /* returns the ordinal difference between two strings :
  *    < 0 if ist1 < ist2
  *    = 0 if ist1 == ist2
  *    > 0 if ist1 > ist2
  */
 static inline int istdiff(const struct ist ist1, const struct ist ist2)
 {
 	struct ist l = ist1;
 	struct ist r = ist2;

 	do {
 		if (!l.len--)
 			return -r.len;
 		if (!r.len--)
 			return 1;
 	} while (*l.ptr++ == *r.ptr++);

 	return *(unsigned char *)(l.ptr - 1) - *(unsigned char *)(r.ptr - 1);
 }

 /* returns non-zero if <ist1> starts like <ist2> (empty strings do match) */
 static inline int istmatch(const struct ist ist1, const struct ist ist2)
 {
 	struct ist l = ist1;
 	struct ist r = ist2;

 	if (l.len < r.len)
 		return 0;

 	while (r.len--) {
 		if (*l.ptr++ != *r.ptr++)
 			return 0;
 	}
 	return 1;
 }

 /* returns non-zero if <ist1> starts like <ist2> on the first <count>
  * characters (empty strings do match).
  */
 static inline int istnmatch(const struct ist ist1, const struct ist ist2, size_t count)
 {
 	struct ist l = ist1;
 	struct ist r = ist2;

 	if (l.len > count)
 		l.len = count;
 	if (r.len > count)
 		r.len = count;
 	return istmatch(l, r);
 }

 /* returns non-zero if <ist1> equals <ist2> (empty strings are equal) */
 static inline int isteq(const struct ist ist1, const struct ist ist2)
 {
 	struct ist l = ist1;
 	struct ist r = ist2;

 	if (l.len != r.len)
 		return 0;

 	while (l.len--) {
 		if (*l.ptr++ != *r.ptr++)
 			return 0;
 	}
 	return 1;
 }

 /* returns non-zero if <ist1> equals <ist2> on the first <count> characters
  * (empty strings are equal).
  */
 static inline int istneq(const struct ist ist1, const struct ist ist2, size_t count)
 {
 	struct ist l = ist1;
 	struct ist r = ist2;

 	if (l.len > count)
 		l.len = count;
 	if (r.len > count)
 		r.len = count;
 	return isteq(l, r);
 }

 /* copies <src> over <dst> for a maximum of <count> bytes. Returns the number
  * of characters copied (src.len), or -1 if it does not fit. In all cases, the
  * contents are copied prior to reporting an error, so that the destination
  * at least contains a valid but truncated string.
  */
 static inline ssize_t istcpy(struct ist *dst, const struct ist src, size_t count)
 {
 	dst->len = 0;

 	if (count > src.len)
 		count = src.len;

 	while (dst->len < count) {
 		dst->ptr[dst->len] = src.ptr[dst->len];
 		dst->len++;
 	}

 	if (dst->len == src.len)
 		return src.len;

 	return -1;
 }

 /* copies <src> over <dst> for a maximum of <count> bytes. Returns the number
  * of characters copied, or -1 if it does not fit. A (possibly truncated) valid
  * copy of <src> is always left into <dst>, and a trailing \0 is appended as
  * long as <count> is not null, even if that results in reducing the string by
  * one character.
  */
 static inline ssize_t istscpy(struct ist *dst, const struct ist src, size_t count)
 {
 	dst->len = 0;

 	if (!count)
 		goto fail;

 	if (count > src.len)
 		count = src.len + 1;

 	while (dst->len < count - 1) {
 		dst->ptr[dst->len] = src.ptr[dst->len];
 		dst->len++;
 	}

 	dst->ptr[dst->len] = 0;
 	if (dst->len == src.len)
 		return src.len;
  fail:
 	return -1;
 }

 /* appends <src> after <dst> for a maximum of <count> total bytes in <dst> after
  * the copy. <dst> is assumed to be <count> or less before the call. The new
  * string's length is returned, or -1 if a truncation happened. In all cases,
  * the contents are copied prior to reporting an error, so that the destination
  * at least contains a valid but truncated string.
  */
 static inline ssize_t istcat(struct ist *dst, const struct ist src, size_t count)
 {
 	const char *s = src.ptr;

 	while (dst->len < count && s != src.ptr + src.len)
 		dst->ptr[dst->len++] = *s++;

 	if (s == src.ptr + src.len)
 		return dst->len;

 	return -1;
 }

 /* appends <src> after <dst> for a maximum of <count> total bytes in <dst> after
  * the copy. <dst> is assumed to be <count> or less before the call. The new
  * string's length is returned, or -1 if a truncation happened. In all cases,
  * the contents are copied prior to reporting an error, so that the destination
  * at least contains a valid but truncated string.
  */
 static inline ssize_t istscat(struct ist *dst, const struct ist src, size_t count)
 {
 	const char *s = src.ptr;

 	if (!count)
 		goto fail;

 	while (dst->len < count - 1 && s != src.ptr + src.len) {
 		dst->ptr[dst->len++] = *s++;
 	}

 	dst->ptr[dst->len] = 0;
 	if (s == src.ptr + src.len)
 		return dst->len;
  fail:
 	return -1;
 }

 /* looks for first occurrence of character <chr> in string <ist>. Returns the
  * pointer if found, or NULL if not found.
  */
 static inline char *istchr(const struct ist ist, char chr)
 {
 	char *s = ist.ptr;

 	do {
 		if (s >= ist.ptr + ist.len)
 			return NULL;
 	} while (*s++ != chr);
 	return s - 1;
 }

 /* looks for first occurrence of character <chr> in string <ist> and returns
  * the tail of the string starting with this character, or (ist.end,0) if not
  * found.
  */
 static inline struct ist istfind(const struct ist ist, char chr)
 {
 	struct ist ret = ist;

 	while (ret.len--) {
 		if (*ret.ptr++ == chr)
 			return ist2(ret.ptr - 1, ret.len + 1);
 	}
 	return ist2(ret.ptr, 0);
 }

 /* looks for first occurrence of character different from <chr> in string <ist>
  * and returns the tail of the string starting at this character, or (ist_end,0)
  * if not found.
  */
 static inline struct ist istskip(const struct ist ist, char chr)
 {
 	struct ist ret = ist;

 	while (ret.len--) {
 		if (*ret.ptr++ != chr)
 			return ist2(ret.ptr - 1, ret.len + 1);
 	}
 	return ist2(ret.ptr, 0);
 }

 /* looks for first occurrence of string <pat> in string <ist> and returns the
  * tail of the string starting at this position, or (NULL,0) if not found. The
  * empty pattern is found everywhere.
  */
 static inline struct ist istist(const struct ist ist, const struct ist pat)
 {
 	struct ist ret = ist;
 	size_t pos;

 	if (!pat.len)
 		return ret;

 	while (1) {
 	loop:
 		ret = istfind(ret, *pat.ptr);
 		if (ret.len < pat.len)
 			break;

 		/* ret.len >= 1, pat.len >= 1 and *ret.ptr == *pat.ptr */

 		ret = istnext(ret);
 		for (pos = 0; pos < pat.len - 1; ) {
 			++pos;
 			if (ret.ptr[pos - 1] != pat.ptr[pos])
 				goto loop;
 		}
 		return ist2(ret.ptr - 1, ret.len + 1);
 	}
 	return ist2(NULL, 0);
 }

 #endif
	/*
	* include/common/ist.h
	* Very simple indirect string manipulation functions.
	*
	* Copyright (C) 2014-2017 Willy Tarreau - w@1wt.eu
	*
	* Permission is hereby granted, free of charge, to any person obtaining
	* a copy of this software and associated documentation files (the
	* "Software"), to deal in the Software without restriction, including
	* without limitation the rights to use, copy, modify, merge, publish,
	* distribute, sublicense, and/or sell copies of the Software, and to
	* permit persons to whom the Software is furnished to do so, subject to
	* the following conditions:
	*
	* The above copyright notice and this permission notice shall be
	* included in all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
	* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
	* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
	* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
	* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
	* OTHER DEALINGS IN THE SOFTWARE.
	*/

	#ifndef _COMMON_IST_H
	#define _COMMON_IST_H

	#include <string.h>

	#include <common/config.h>

	/* This string definition will most often be used to represent a read-only
	* string returned from a function, based on the starting point and its length
	* in bytes. No storage is provided, only a pointer and a length. The types
	* here are important as we only want to have 2 native machine words there so
	* that on modern architectures the compiler is capable of efficiently
	* returning a register pair without having to allocate stack room from the
	* caller. This is done with -freg-struct which is often enabled by default.
	*/
	struct ist {
	char *ptr;
	size_t len;
	};

	/* makes a constant ist from a constant string, for use in array declarations */
	#define IST(str) { .ptr = str "", .len = (sizeof str "") - 1 }

	/* makes an ist from a regular zero terminated string. Null has length 0.
	* Constants are detected and replaced with constant initializers. Other values
	* are measured by hand without strlen() as it's much cheaper and inlinable on
	* small strings. The construct is complex because we must never call
	* __builtin_strlen() with an expression otherwise it involves a real
	* measurement.
	*/
	#if __GNUC__ >= 4
	// gcc >= 4 detects constant propagation of str through __x and resolves the
	// length of constant strings easily.
	#define ist(str) ({ \
	char __x = (void )(str); \
	(struct ist){ \
	.ptr = __x, \
	.len = __builtin_constant_p(str) ? \
	((void )str == (void )0) ? 0 : \
	__builtin_strlen(__x) : \
	({ \
	size_t __l = 0; \
	if (__x) for (__l--; __x[++__l]; ) ; \
	__l; \
	}) \
	}; \
	})
	#else
	// gcc < 4 can't do this, and the side effect is a warning each time a NULL is
	// passed to ist() due to the check on __builtin_strlen(). It doesn't have the
	// ability to know that this code is never called.
	#define ist(str) ({ \
	char __x = (void )(str); \
	(struct ist){ \
	.ptr = __x, \
	.len = __builtin_constant_p(str) ? \
	((void )str == (void )0) ? 0 : \
	__builtin_strlen(str) : \
	({ \
	size_t __l = 0; \
	if (__x) for (__l--; __x[++__l]; ) ; \
	__l; \
	}) \
	}; \
	})
	#endif

	/* makes an ist struct from a string and a length */
	static inline struct ist ist2(const void *ptr, size_t len)
	{
	return (struct ist){ .ptr = (char *)ptr, .len = len };
	}

	/* returns the length of the string */
	static inline size_t istlen(const struct ist ist)
	{
	return ist.len;
	}

	/* skips to next character in the string, always stops at the end */
	static inline struct ist istnext(const struct ist ist)
	{
	struct ist ret = ist;

	if (ret.len) {
	ret.len--;
	ret.ptr++;
	}
	return ret;
	}

	/* copies the contents from string <ist> to buffer <buf> and adds a trailing
	* zero. The caller must ensure <buf> is large enough.
	*/
	static inline struct ist istpad(void *buf, const struct ist ist)
	{
	struct ist ret = { .ptr = buf, .len = ist.len };

	for (ret.len = 0; ret.len < ist.len; ret.len++)
	ret.ptr[ret.len] = ist.ptr[ret.len];

	ret.ptr[ret.len] = 0;
	return ret;
	}

	/* trims string <ist> to no more than <size> characters. The string is
	* returned.
	*/
	static inline struct ist isttrim(const struct ist ist, size_t size)
	{
	struct ist ret = ist;

	if (ret.len > size)
	ret.len = size;
	return ret;
	}

	/* trims string <ist> to no more than <size>-1 characters and ensures that a
	* zero is placed after <ist.len> (possibly reduced by one) and before <size>,
	* unless <size> is already zero. The string is returned. This is mostly aimed
	* at building printable strings that need to be zero-terminated.
	*/
	static inline struct ist istzero(const struct ist ist, size_t size)
	{
	struct ist ret = ist;

	if (!size)
	ret.len = 0;
	else {
	if (ret.len > size - 1)
	ret.len = size - 1;
	ret.ptr[ret.len] = 0;
	}
	return ret;
	}

	/* returns the ordinal difference between two strings :
	* < 0 if ist1 < ist2
	* = 0 if ist1 == ist2
	* > 0 if ist1 > ist2
	*/
	static inline int istdiff(const struct ist ist1, const struct ist ist2)
	{
	struct ist l = ist1;
	struct ist r = ist2;

	do {
	if (!l.len--)
	return -r.len;
	if (!r.len--)
	return 1;
	} while (l.ptr++ == r.ptr++);

	return (unsigned char )(l.ptr - 1) - (unsigned char )(r.ptr - 1);
	}

	/* returns non-zero if <ist1> starts like <ist2> (empty strings do match) */
	static inline int istmatch(const struct ist ist1, const struct ist ist2)
	{
	struct ist l = ist1;
	struct ist r = ist2;

	if (l.len < r.len)
	return 0;

	while (r.len--) {
	if (l.ptr++ != r.ptr++)
	return 0;
	}
	return 1;
	}

	/* returns non-zero if <ist1> starts like <ist2> on the first <count>
	* characters (empty strings do match).
	*/
	static inline int istnmatch(const struct ist ist1, const struct ist ist2, size_t count)
	{
	struct ist l = ist1;
	struct ist r = ist2;

	if (l.len > count)
	l.len = count;
	if (r.len > count)
	r.len = count;
	return istmatch(l, r);
	}

	/* returns non-zero if <ist1> equals <ist2> (empty strings are equal) */
	static inline int isteq(const struct ist ist1, const struct ist ist2)
	{
	struct ist l = ist1;
	struct ist r = ist2;

	if (l.len != r.len)
	return 0;

	while (l.len--) {
	if (l.ptr++ != r.ptr++)
	return 0;
	}
	return 1;
	}

	/* returns non-zero if <ist1> equals <ist2> on the first <count> characters
	* (empty strings are equal).
	*/
	static inline int istneq(const struct ist ist1, const struct ist ist2, size_t count)
	{
	struct ist l = ist1;
	struct ist r = ist2;

	if (l.len > count)
	l.len = count;
	if (r.len > count)
	r.len = count;
	return isteq(l, r);
	}

	/* copies <src> over <dst> for a maximum of <count> bytes. Returns the number
	* of characters copied (src.len), or -1 if it does not fit. In all cases, the
	* contents are copied prior to reporting an error, so that the destination
	* at least contains a valid but truncated string.
	*/
	static inline ssize_t istcpy(struct ist *dst, const struct ist src, size_t count)
	{
	dst->len = 0;

	if (count > src.len)
	count = src.len;

	while (dst->len < count) {
	dst->ptr[dst->len] = src.ptr[dst->len];
	dst->len++;
	}

	if (dst->len == src.len)
	return src.len;

	return -1;
	}

	/* copies <src> over <dst> for a maximum of <count> bytes. Returns the number
	* of characters copied, or -1 if it does not fit. A (possibly truncated) valid
	* copy of <src> is always left into <dst>, and a trailing \0 is appended as
	* long as <count> is not null, even if that results in reducing the string by
	* one character.
	*/
	static inline ssize_t istscpy(struct ist *dst, const struct ist src, size_t count)
	{
	dst->len = 0;

	if (!count)
	goto fail;

	if (count > src.len)
	count = src.len + 1;

	while (dst->len < count - 1) {
	dst->ptr[dst->len] = src.ptr[dst->len];
	dst->len++;
	}

	dst->ptr[dst->len] = 0;
	if (dst->len == src.len)
	return src.len;
	fail:
	return -1;
	}

	/* appends <src> after <dst> for a maximum of <count> total bytes in <dst> after
	* the copy. <dst> is assumed to be <count> or less before the call. The new
	* string's length is returned, or -1 if a truncation happened. In all cases,
	* the contents are copied prior to reporting an error, so that the destination
	* at least contains a valid but truncated string.
	*/
	static inline ssize_t istcat(struct ist *dst, const struct ist src, size_t count)
	{
	const char *s = src.ptr;

	while (dst->len < count && s != src.ptr + src.len)
	dst->ptr[dst->len++] = *s++;

	if (s == src.ptr + src.len)
	return dst->len;

	return -1;
	}

	/* appends <src> after <dst> for a maximum of <count> total bytes in <dst> after
	* the copy. <dst> is assumed to be <count> or less before the call. The new
	* string's length is returned, or -1 if a truncation happened. In all cases,
	* the contents are copied prior to reporting an error, so that the destination
	* at least contains a valid but truncated string.
	*/
	static inline ssize_t istscat(struct ist *dst, const struct ist src, size_t count)
	{
	const char *s = src.ptr;

	if (!count)
	goto fail;

	while (dst->len < count - 1 && s != src.ptr + src.len) {
	dst->ptr[dst->len++] = *s++;
	}

	dst->ptr[dst->len] = 0;
	if (s == src.ptr + src.len)
	return dst->len;
	fail:
	return -1;
	}

	/* looks for first occurrence of character <chr> in string <ist>. Returns the
	* pointer if found, or NULL if not found.
	*/
	static inline char *istchr(const struct ist ist, char chr)
	{
	char *s = ist.ptr;

	do {
	if (s >= ist.ptr + ist.len)
	return NULL;
	} while (*s++ != chr);
	return s - 1;
	}

	/* looks for first occurrence of character <chr> in string <ist> and returns
	* the tail of the string starting with this character, or (ist.end,0) if not
	* found.
	*/
	static inline struct ist istfind(const struct ist ist, char chr)
	{
	struct ist ret = ist;

	while (ret.len--) {
	if (*ret.ptr++ == chr)
	return ist2(ret.ptr - 1, ret.len + 1);
	}
	return ist2(ret.ptr, 0);
	}

	/* looks for first occurrence of character different from <chr> in string <ist>
	* and returns the tail of the string starting at this character, or (ist_end,0)
	* if not found.
	*/
	static inline struct ist istskip(const struct ist ist, char chr)
	{
	struct ist ret = ist;

	while (ret.len--) {
	if (*ret.ptr++ != chr)
	return ist2(ret.ptr - 1, ret.len + 1);
	}
	return ist2(ret.ptr, 0);
	}

	/* looks for first occurrence of string <pat> in string <ist> and returns the
	* tail of the string starting at this position, or (NULL,0) if not found. The
	* empty pattern is found everywhere.
	*/
	static inline struct ist istist(const struct ist ist, const struct ist pat)
	{
	struct ist ret = ist;
	size_t pos;

	if (!pat.len)
	return ret;

	while (1) {
	loop:
	ret = istfind(ret, *pat.ptr);
	if (ret.len < pat.len)
	break;

	/* ret.len >= 1, pat.len >= 1 and ret.ptr == pat.ptr */

	ret = istnext(ret);
	for (pos = 0; pos < pat.len - 1; ) {
	++pos;
	if (ret.ptr[pos - 1] != pat.ptr[pos])
	goto loop;
	}
	return ist2(ret.ptr - 1, ret.len + 1);
	}
	return ist2(NULL, 0);
	}

	#endif