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redict/src/listpack.c
antirez efcbc01fbd Remove warning from lpGet snprintf().
2018-03-01 15:26:27 +01:00

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/* Listpack -- A lists of strings serialization format
*
* This file implements the specification you can find at:
*
* https://github.com/antirez/listpack
*
* Copyright (c) 2017, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdint.h>
#include <limits.h>
#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "listpack.h"
#include "listpack_malloc.h"
#define LP_HDR_SIZE 6 /* 32 bit total len + 16 bit number of elements. */
#define LP_HDR_NUMELE_UNKNOWN UINT16_MAX
#define LP_MAX_INT_ENCODING_LEN 9
#define LP_MAX_BACKLEN_SIZE 5
#define LP_MAX_ENTRY_BACKLEN 34359738367ULL
#define LP_ENCODING_INT 0
#define LP_ENCODING_STRING 1
#define LP_ENCODING_7BIT_UINT 0
#define LP_ENCODING_7BIT_UINT_MASK 0x80
#define LP_ENCODING_IS_7BIT_UINT(byte) (((byte)&LP_ENCODING_7BIT_UINT_MASK)==LP_ENCODING_7BIT_UINT)
#define LP_ENCODING_6BIT_STR 0x80
#define LP_ENCODING_6BIT_STR_MASK 0xC0
#define LP_ENCODING_IS_6BIT_STR(byte) (((byte)&LP_ENCODING_6BIT_STR_MASK)==LP_ENCODING_6BIT_STR)
#define LP_ENCODING_13BIT_INT 0xC0
#define LP_ENCODING_13BIT_INT_MASK 0xE0
#define LP_ENCODING_IS_13BIT_INT(byte) (((byte)&LP_ENCODING_13BIT_INT_MASK)==LP_ENCODING_13BIT_INT)
#define LP_ENCODING_12BIT_STR 0xE0
#define LP_ENCODING_12BIT_STR_MASK 0xF0
#define LP_ENCODING_IS_12BIT_STR(byte) (((byte)&LP_ENCODING_12BIT_STR_MASK)==LP_ENCODING_12BIT_STR)
#define LP_ENCODING_16BIT_INT 0xF1
#define LP_ENCODING_16BIT_INT_MASK 0xFF
#define LP_ENCODING_IS_16BIT_INT(byte) (((byte)&LP_ENCODING_16BIT_INT_MASK)==LP_ENCODING_16BIT_INT)
#define LP_ENCODING_24BIT_INT 0xF2
#define LP_ENCODING_24BIT_INT_MASK 0xFF
#define LP_ENCODING_IS_24BIT_INT(byte) (((byte)&LP_ENCODING_24BIT_INT_MASK)==LP_ENCODING_24BIT_INT)
#define LP_ENCODING_32BIT_INT 0xF3
#define LP_ENCODING_32BIT_INT_MASK 0xFF
#define LP_ENCODING_IS_32BIT_INT(byte) (((byte)&LP_ENCODING_32BIT_INT_MASK)==LP_ENCODING_32BIT_INT)
#define LP_ENCODING_64BIT_INT 0xF4
#define LP_ENCODING_64BIT_INT_MASK 0xFF
#define LP_ENCODING_IS_64BIT_INT(byte) (((byte)&LP_ENCODING_64BIT_INT_MASK)==LP_ENCODING_64BIT_INT)
#define LP_ENCODING_32BIT_STR 0xF0
#define LP_ENCODING_32BIT_STR_MASK 0xFF
#define LP_ENCODING_IS_32BIT_STR(byte) (((byte)&LP_ENCODING_32BIT_STR_MASK)==LP_ENCODING_32BIT_STR)
#define LP_EOF 0xFF
#define LP_ENCODING_6BIT_STR_LEN(p) ((p)[0] & 0x3F)
#define LP_ENCODING_12BIT_STR_LEN(p) ((((p)[0] & 0xF) << 8) | (p)[1])
#define LP_ENCODING_32BIT_STR_LEN(p) (((uint32_t)(p)[1]<<0) | \
((uint32_t)(p)[2]<<8) | \
((uint32_t)(p)[3]<<16) | \
((uint32_t)(p)[4]<<24))
#define lpGetTotalBytes(p) (((uint32_t)(p)[0]<<0) | \
((uint32_t)(p)[1]<<8) | \
((uint32_t)(p)[2]<<16) | \
((uint32_t)(p)[3]<<24))
#define lpGetNumElements(p) (((uint32_t)(p)[4]<<0) | \
((uint32_t)(p)[5]<<8))
#define lpSetTotalBytes(p,v) do { \
(p)[0] = (v)&0xff; \
(p)[1] = ((v)>>8)&0xff; \
(p)[2] = ((v)>>16)&0xff; \
(p)[3] = ((v)>>24)&0xff; \
} while(0)
#define lpSetNumElements(p,v) do { \
(p)[4] = (v)&0xff; \
(p)[5] = ((v)>>8)&0xff; \
} while(0)
/* Convert a string into a signed 64 bit integer.
* The function returns 1 if the string could be parsed into a (non-overflowing)
* signed 64 bit int, 0 otherwise. The 'value' will be set to the parsed value
* when the function returns success.
*
* Note that this function demands that the string strictly represents
* a int64 value: no spaces or other characters before or after the string
* representing the number are accepted, nor zeroes at the start if not
* for the string "0" representing the zero number.
*
* Because of its strictness, it is safe to use this function to check if
* you can convert a string into a long long, and obtain back the string
* from the number without any loss in the string representation. *
*
* -----------------------------------------------------------------------------
*
* Credits: this function was adapted from the Redis source code, file
* "utils.c", function string2ll(), and is copyright:
*
* Copyright(C) 2011, Pieter Noordhuis
* Copyright(C) 2011, Salvatore Sanfilippo
*
* The function is released under the BSD 3-clause license.
*/
int lpStringToInt64(const char *s, unsigned long slen, int64_t *value) {
const char *p = s;
unsigned long plen = 0;
int negative = 0;
uint64_t v;
if (plen == slen)
return 0;
/* Special case: first and only digit is 0. */
if (slen == 1 && p[0] == '0') {
if (value != NULL) *value = 0;
return 1;
}
if (p[0] == '-') {
negative = 1;
p++; plen++;
/* Abort on only a negative sign. */
if (plen == slen)
return 0;
}
/* First digit should be 1-9, otherwise the string should just be 0. */
if (p[0] >= '1' && p[0] <= '9') {
v = p[0]-'0';
p++; plen++;
} else if (p[0] == '0' && slen == 1) {
*value = 0;
return 1;
} else {
return 0;
}
while (plen < slen && p[0] >= '0' && p[0] <= '9') {
if (v > (UINT64_MAX / 10)) /* Overflow. */
return 0;
v *= 10;
if (v > (UINT64_MAX - (p[0]-'0'))) /* Overflow. */
return 0;
v += p[0]-'0';
p++; plen++;
}
/* Return if not all bytes were used. */
if (plen < slen)
return 0;
if (negative) {
if (v > ((uint64_t)(-(INT64_MIN+1))+1)) /* Overflow. */
return 0;
if (value != NULL) *value = -v;
} else {
if (v > INT64_MAX) /* Overflow. */
return 0;
if (value != NULL) *value = v;
}
return 1;
}
/* Create a new, empty listpack.
* On success the new listpack is returned, otherwise an error is returned. */
unsigned char *lpNew(void) {
unsigned char *lp = lp_malloc(LP_HDR_SIZE+1);
if (lp == NULL) return NULL;
lpSetTotalBytes(lp,LP_HDR_SIZE+1);
lpSetNumElements(lp,0);
lp[LP_HDR_SIZE] = LP_EOF;
return lp;
}
/* Free the specified listpack. */
void lpFree(unsigned char *lp) {
lp_free(lp);
}
/* Given an element 'ele' of size 'size', determine if the element can be
* represented inside the listpack encoded as integer, and returns
* LP_ENCODING_INT if so. Otherwise returns LP_ENCODING_STR if no integer
* encoding is possible.
*
* If the LP_ENCODING_INT is returned, the function stores the integer encoded
* representation of the element in the 'intenc' buffer.
*
* Regardless of the returned encoding, 'enclen' is populated by reference to
* the number of bytes that the string or integer encoded element will require
* in order to be represented. */
int lpEncodeGetType(unsigned char *ele, uint32_t size, unsigned char *intenc, uint64_t *enclen) {
int64_t v;
if (lpStringToInt64((const char*)ele, size, &v)) {
if (v >= 0 && v <= 127) {
/* Single byte 0-127 integer. */
intenc[0] = v;
*enclen = 1;
} else if (v >= -4096 && v <= 4095) {
/* 13 bit integer. */
if (v < 0) v = ((int64_t)1<<13)+v;
intenc[0] = (v>>8)|LP_ENCODING_13BIT_INT;
intenc[1] = v&0xff;
*enclen = 2;
} else if (v >= -32768 && v <= 32767) {
/* 16 bit integer. */
if (v < 0) v = ((int64_t)1<<16)+v;
intenc[0] = LP_ENCODING_16BIT_INT;
intenc[1] = v&0xff;
intenc[2] = v>>8;
*enclen = 3;
} else if (v >= -8388608 && v <= 8388607) {
/* 24 bit integer. */
if (v < 0) v = ((int64_t)1<<24)+v;
intenc[0] = LP_ENCODING_24BIT_INT;
intenc[1] = v&0xff;
intenc[2] = (v>>8)&0xff;
intenc[3] = v>>16;
*enclen = 4;
} else if (v >= -2147483648 && v <= 2147483647) {
/* 32 bit integer. */
if (v < 0) v = ((int64_t)1<<32)+v;
intenc[0] = LP_ENCODING_32BIT_INT;
intenc[1] = v&0xff;
intenc[2] = (v>>8)&0xff;
intenc[3] = (v>>16)&0xff;
intenc[4] = v>>24;
*enclen = 5;
} else {
/* 64 bit integer. */
uint64_t uv = v;
intenc[0] = LP_ENCODING_64BIT_INT;
intenc[1] = uv&0xff;
intenc[2] = (uv>>8)&0xff;
intenc[3] = (uv>>16)&0xff;
intenc[4] = (uv>>24)&0xff;
intenc[5] = (uv>>32)&0xff;
intenc[6] = (uv>>40)&0xff;
intenc[7] = (uv>>48)&0xff;
intenc[8] = uv>>56;
*enclen = 9;
}
return LP_ENCODING_INT;
} else {
if (size < 64) *enclen = 1+size;
else if (size < 4096) *enclen = 2+size;
else *enclen = 5+size;
return LP_ENCODING_STRING;
}
}
/* Store a reverse-encoded variable length field, representing the length
* of the previous element of size 'l', in the target buffer 'buf'.
* The function returns the number of bytes used to encode it, from
* 1 to 5. If 'buf' is NULL the funciton just returns the number of bytes
* needed in order to encode the backlen. */
unsigned long lpEncodeBacklen(unsigned char *buf, uint64_t l) {
if (l <= 127) {
if (buf) buf[0] = l;
return 1;
} else if (l < 16383) {
if (buf) {
buf[0] = l>>7;
buf[1] = (l&127)|128;
}
return 2;
} else if (l < 2097151) {
if (buf) {
buf[0] = l>>14;
buf[1] = ((l>>7)&127)|128;
buf[2] = (l&127)|128;
}
return 3;
} else if (l < 268435455) {
if (buf) {
buf[0] = l>>21;
buf[1] = ((l>>14)&127)|128;
buf[2] = ((l>>7)&127)|128;
buf[3] = (l&127)|128;
}
return 4;
} else {
if (buf) {
buf[0] = l>>28;
buf[1] = ((l>>21)&127)|128;
buf[2] = ((l>>14)&127)|128;
buf[3] = ((l>>7)&127)|128;
buf[4] = (l&127)|128;
}
return 5;
}
}
/* Decode the backlen and returns it. If the encoding looks invalid (more than
* 5 bytes are used), UINT64_MAX is returned to report the problem. */
uint64_t lpDecodeBacklen(unsigned char *p) {
uint64_t val = 0;
uint64_t shift = 0;
do {
val |= (uint64_t)(p[0] & 127) << shift;
if (!(p[0] & 128)) break;
shift += 7;
p--;
if (shift > 28) return UINT64_MAX;
} while(1);
return val;
}
/* Encode the string element pointed by 's' of size 'len' in the target
* buffer 's'. The function should be called with 'buf' having always enough
* space for encoding the string. This is done by calling lpEncodeGetType()
* before calling this function. */
void lpEncodeString(unsigned char *buf, unsigned char *s, uint32_t len) {
if (len < 64) {
buf[0] = len | LP_ENCODING_6BIT_STR;
memcpy(buf+1,s,len);
} else if (len < 4096) {
buf[0] = (len >> 8) | LP_ENCODING_12BIT_STR;
buf[1] = len & 0xff;
memcpy(buf+2,s,len);
} else {
buf[0] = LP_ENCODING_32BIT_STR;
buf[1] = len & 0xff;
buf[2] = (len >> 8) & 0xff;
buf[3] = (len >> 16) & 0xff;
buf[4] = (len >> 24) & 0xff;
memcpy(buf+5,s,len);
}
}
/* Return the encoded length of the listpack element pointed by 'p'. If the
* element encoding is wrong then 0 is returned. */
uint32_t lpCurrentEncodedSize(unsigned char *p) {
if (LP_ENCODING_IS_7BIT_UINT(p[0])) return 1;
if (LP_ENCODING_IS_6BIT_STR(p[0])) return 1+LP_ENCODING_6BIT_STR_LEN(p);
if (LP_ENCODING_IS_13BIT_INT(p[0])) return 2;
if (LP_ENCODING_IS_16BIT_INT(p[0])) return 3;
if (LP_ENCODING_IS_24BIT_INT(p[0])) return 4;
if (LP_ENCODING_IS_32BIT_INT(p[0])) return 5;
if (LP_ENCODING_IS_64BIT_INT(p[0])) return 9;
if (LP_ENCODING_IS_12BIT_STR(p[0])) return 2+LP_ENCODING_12BIT_STR_LEN(p);
if (LP_ENCODING_IS_32BIT_STR(p[0])) return 5+LP_ENCODING_32BIT_STR_LEN(p);
if (p[0] == LP_EOF) return 1;
return 0;
}
/* Skip the current entry returning the next. It is invalid to call this
* function if the current element is the EOF element at the end of the
* listpack, however, while this function is used to implement lpNext(),
* it does not return NULL when the EOF element is encountered. */
unsigned char *lpSkip(unsigned char *p) {
unsigned long entrylen = lpCurrentEncodedSize(p);
entrylen += lpEncodeBacklen(NULL,entrylen);
p += entrylen;
return p;
}
/* If 'p' points to an element of the listpack, calling lpNext() will return
* the pointer to the next element (the one on the right), or NULL if 'p'
* already pointed to the last element of the listpack. */
unsigned char *lpNext(unsigned char *lp, unsigned char *p) {
((void) lp); /* lp is not used for now. However lpPrev() uses it. */
p = lpSkip(p);
if (p[0] == LP_EOF) return NULL;
return p;
}
/* If 'p' points to an element of the listpack, calling lpPrev() will return
* the pointer to the preivous element (the one on the left), or NULL if 'p'
* already pointed to the first element of the listpack. */
unsigned char *lpPrev(unsigned char *lp, unsigned char *p) {
if (p-lp == LP_HDR_SIZE) return NULL;
p--; /* Seek the first backlen byte of the last element. */
uint64_t prevlen = lpDecodeBacklen(p);
prevlen += lpEncodeBacklen(NULL,prevlen);
return p-prevlen+1; /* Seek the first byte of the previous entry. */
}
/* Return a pointer to the first element of the listpack, or NULL if the
* listpack has no elements. */
unsigned char *lpFirst(unsigned char *lp) {
lp += LP_HDR_SIZE; /* Skip the header. */
if (lp[0] == LP_EOF) return NULL;
return lp;
}
/* Return a pointer to the last element of the listpack, or NULL if the
* listpack has no elements. */
unsigned char *lpLast(unsigned char *lp) {
unsigned char *p = lp+lpGetTotalBytes(lp)-1; /* Seek EOF element. */
return lpPrev(lp,p); /* Will return NULL if EOF is the only element. */
}
/* Return the number of elements inside the listpack. This function attempts
* to use the cached value when within range, otherwise a full scan is
* needed. As a side effect of calling this function, the listpack header
* could be modified, because if the count is found to be already within
* the 'numele' header field range, the new value is set. */
uint32_t lpLength(unsigned char *lp) {
uint32_t numele = lpGetNumElements(lp);
if (numele != LP_HDR_NUMELE_UNKNOWN) return numele;
/* Too many elements inside the listpack. We need to scan in order
* to get the total number. */
uint32_t count = 0;
unsigned char *p = lpFirst(lp);
while(p) {
count++;
p = lpNext(lp,p);
}
/* If the count is again within range of the header numele field,
* set it. */
if (count < LP_HDR_NUMELE_UNKNOWN) lpSetNumElements(lp,count);
return count;
}
/* Return the listpack element pointed by 'p'.
*
* The function changes behavior depending on the passed 'intbuf' value.
* Specifically, if 'intbuf' is NULL:
*
* If the element is internally encoded as an integer, the function returns
* NULL and populates the integer value by reference in 'count'. Otherwise if
* the element is encoded as a string a pointer to the string (pointing inside
* the listpack itself) is returned, and 'count' is set to the length of the
* string.
*
* If instead 'intbuf' points to a buffer passed by the caller, that must be
* at least LP_INTBUF_SIZE bytes, the function always returns the element as
* it was a string (returning the pointer to the string and setting the
* 'count' argument to the string length by reference). However if the element
* is encoded as an integer, the 'intbuf' buffer is used in order to store
* the string representation.
*
* The user should use one or the other form depending on what the value will
* be used for. If there is immediate usage for an integer value returned
* by the function, than to pass a buffer (and convert it back to a number)
* is of course useless.
*
* If the function is called against a badly encoded ziplist, so that there
* is no valid way to parse it, the function returns like if there was an
* integer encoded with value 12345678900000000 + <unrecognized byte>, this may
* be an hint to understand that something is wrong. To crash in this case is
* not sensible because of the different requirements of the application using
* this lib.
*
* Similarly, there is no error returned since the listpack normally can be
* assumed to be valid, so that would be a very high API cost. However a function
* in order to check the integrity of the listpack at load time is provided,
* check lpIsValid(). */
unsigned char *lpGet(unsigned char *p, int64_t *count, unsigned char *intbuf) {
int64_t val;
uint64_t uval, negstart, negmax;
if (LP_ENCODING_IS_7BIT_UINT(p[0])) {
negstart = UINT64_MAX; /* 7 bit ints are always positive. */
negmax = 0;
uval = p[0] & 0x7f;
} else if (LP_ENCODING_IS_6BIT_STR(p[0])) {
*count = LP_ENCODING_6BIT_STR_LEN(p);
return p+1;
} else if (LP_ENCODING_IS_13BIT_INT(p[0])) {
uval = ((p[0]&0x1f)<<8) | p[1];
negstart = (uint64_t)1<<12;
negmax = 8191;
} else if (LP_ENCODING_IS_16BIT_INT(p[0])) {
uval = (uint64_t)p[1] |
(uint64_t)p[2]<<8;
negstart = (uint64_t)1<<15;
negmax = UINT16_MAX;
} else if (LP_ENCODING_IS_24BIT_INT(p[0])) {
uval = (uint64_t)p[1] |
(uint64_t)p[2]<<8 |
(uint64_t)p[3]<<16;
negstart = (uint64_t)1<<23;
negmax = UINT32_MAX>>8;
} else if (LP_ENCODING_IS_32BIT_INT(p[0])) {
uval = (uint64_t)p[1] |
(uint64_t)p[2]<<8 |
(uint64_t)p[3]<<16 |
(uint64_t)p[4]<<24;
negstart = (uint64_t)1<<31;
negmax = UINT32_MAX;
} else if (LP_ENCODING_IS_64BIT_INT(p[0])) {
uval = (uint64_t)p[1] |
(uint64_t)p[2]<<8 |
(uint64_t)p[3]<<16 |
(uint64_t)p[4]<<24 |
(uint64_t)p[5]<<32 |
(uint64_t)p[6]<<40 |
(uint64_t)p[7]<<48 |
(uint64_t)p[8]<<56;
negstart = (uint64_t)1<<63;
negmax = UINT64_MAX;
} else if (LP_ENCODING_IS_12BIT_STR(p[0])) {
*count = LP_ENCODING_12BIT_STR_LEN(p);
return p+2;
} else if (LP_ENCODING_IS_32BIT_STR(p[0])) {
*count = LP_ENCODING_32BIT_STR_LEN(p);
return p+5;
} else {
uval = 12345678900000000ULL + p[0];
negstart = UINT64_MAX;
negmax = 0;
}
/* We reach this code path only for integer encodings.
* Convert the unsigned value to the signed one using two's complement
* rule. */
if (uval >= negstart) {
/* This three steps conversion should avoid undefined behaviors
* in the unsigned -> signed conversion. */
uval = negmax-uval;
val = uval;
val = -val-1;
} else {
val = uval;
}
/* Return the string representation of the integer or the value itself
* depending on intbuf being NULL or not. */
if (intbuf) {
*count = snprintf((char*)intbuf,LP_INTBUF_SIZE,"%lld",(long long)val);
return intbuf;
} else {
*count = val;
return NULL;
}
}
/* Insert, delete or replace the specified element 'ele' of lenght 'len' at
* the specified position 'p', with 'p' being a listpack element pointer
* obtained with lpFirst(), lpLast(), lpIndex(), lpNext(), lpPrev() or
* lpSeek().
*
* The element is inserted before, after, or replaces the element pointed
* by 'p' depending on the 'where' argument, that can be LP_BEFORE, LP_AFTER
* or LP_REPLACE.
*
* If 'ele' is set to NULL, the function removes the element pointed by 'p'
* instead of inserting one.
*
* Returns NULL on out of memory or when the listpack total length would exceed
* the max allowed size of 2^32-1, otherwise the new pointer to the listpack
* holding the new element is returned (and the old pointer passed is no longer
* considered valid)
*
* If 'newp' is not NULL, at the end of a successful call '*newp' will be set
* to the address of the element just added, so that it will be possible to
* continue an interation with lpNext() and lpPrev().
*
* For deletion operations ('ele' set to NULL) 'newp' is set to the next
* element, on the right of the deleted one, or to NULL if the deleted element
* was the last one. */
unsigned char *lpInsert(unsigned char *lp, unsigned char *ele, uint32_t size, unsigned char *p, int where, unsigned char **newp) {
unsigned char intenc[LP_MAX_INT_ENCODING_LEN];
unsigned char backlen[LP_MAX_BACKLEN_SIZE];
uint64_t enclen; /* The length of the encoded element. */
/* An element pointer set to NULL means deletion, which is conceptually
* replacing the element with a zero-length element. So whatever we
* get passed as 'where', set it to LP_REPLACE. */
if (ele == NULL) where = LP_REPLACE;
/* If we need to insert after the current element, we just jump to the
* next element (that could be the EOF one) and handle the case of
* inserting before. So the function will actually deal with just two
* cases: LP_BEFORE and LP_REPLACE. */
if (where == LP_AFTER) {
p = lpSkip(p);
where = LP_BEFORE;
}
/* Store the offset of the element 'p', so that we can obtain its
* address again after a reallocation. */
unsigned long poff = p-lp;
/* Calling lpEncodeGetType() results into the encoded version of the
* element to be stored into 'intenc' in case it is representable as
* an integer: in that case, the function returns LP_ENCODING_INT.
* Otherwise if LP_ENCODING_STR is returned, we'll have to call
* lpEncodeString() to actually write the encoded string on place later.
*
* Whatever the returned encoding is, 'enclen' is populated with the
* length of the encoded element. */
int enctype;
if (ele) {
enctype = lpEncodeGetType(ele,size,intenc,&enclen);
} else {
enctype = -1;
enclen = 0;
}
/* We need to also encode the backward-parsable length of the element
* and append it to the end: this allows to traverse the listpack from
* the end to the start. */
unsigned long backlen_size = ele ? lpEncodeBacklen(backlen,enclen) : 0;
uint64_t old_listpack_bytes = lpGetTotalBytes(lp);
uint32_t replaced_len = 0;
if (where == LP_REPLACE) {
replaced_len = lpCurrentEncodedSize(p);
replaced_len += lpEncodeBacklen(NULL,replaced_len);
}
uint64_t new_listpack_bytes = old_listpack_bytes + enclen + backlen_size
- replaced_len;
if (new_listpack_bytes > UINT32_MAX) return NULL;
/* We now need to reallocate in order to make space or shrink the
* allocation (in case 'when' value is LP_REPLACE and the new element is
* smaller). However we do that before memmoving the memory to
* make room for the new element if the final allocation will get
* larger, or we do it after if the final allocation will get smaller. */
unsigned char *dst = lp + poff; /* May be updated after reallocation. */
/* Realloc before: we need more room. */
if (new_listpack_bytes > old_listpack_bytes) {
if ((lp = lp_realloc(lp,new_listpack_bytes)) == NULL) return NULL;
dst = lp + poff;
}
/* Setup the listpack relocating the elements to make the exact room
* we need to store the new one. */
if (where == LP_BEFORE) {
memmove(dst+enclen+backlen_size,dst,old_listpack_bytes-poff);
} else { /* LP_REPLACE. */
long lendiff = (enclen+backlen_size)-replaced_len;
memmove(dst+replaced_len+lendiff,
dst+replaced_len,
old_listpack_bytes-poff-replaced_len);
}
/* Realloc after: we need to free space. */
if (new_listpack_bytes < old_listpack_bytes) {
if ((lp = lp_realloc(lp,new_listpack_bytes)) == NULL) return NULL;
dst = lp + poff;
}
/* Store the entry. */
if (newp) {
*newp = dst;
/* In case of deletion, set 'newp' to NULL if the next element is
* the EOF element. */
if (!ele && dst[0] == LP_EOF) *newp = NULL;
}
if (ele) {
if (enctype == LP_ENCODING_INT) {
memcpy(dst,intenc,enclen);
} else {
lpEncodeString(dst,ele,size);
}
dst += enclen;
memcpy(dst,backlen,backlen_size);
dst += backlen_size;
}
/* Update header. */
if (where != LP_REPLACE || ele == NULL) {
uint32_t num_elements = lpGetNumElements(lp);
if (num_elements != LP_HDR_NUMELE_UNKNOWN) {
if (ele)
lpSetNumElements(lp,num_elements+1);
else
lpSetNumElements(lp,num_elements-1);
}
}
lpSetTotalBytes(lp,new_listpack_bytes);
return lp;
}
/* Append the specified element 'ele' of lenght 'len' at the end of the
* listpack. It is implemented in terms of lpInsert(), so the return value is
* the same as lpInsert(). */
unsigned char *lpAppend(unsigned char *lp, unsigned char *ele, uint32_t size) {
uint64_t listpack_bytes = lpGetTotalBytes(lp);
unsigned char *eofptr = lp + listpack_bytes - 1;
return lpInsert(lp,ele,size,eofptr,LP_BEFORE,NULL);
}
/* Remove the element pointed by 'p', and return the resulting listpack.
* If 'newp' is not NULL, the next element pointer (to the right of the
* deleted one) is returned by reference. If the deleted element was the
* last one, '*newp' is set to NULL. */
unsigned char *lpDelete(unsigned char *lp, unsigned char *p, unsigned char **newp) {
return lpInsert(lp,NULL,0,p,LP_REPLACE,newp);
}
/* Return the total number of bytes the listpack is composed of. */
uint32_t lpBytes(unsigned char *lp) {
return lpGetTotalBytes(lp);
}
/* Seek the specified element and returns the pointer to the seeked element.
* Positive indexes specify the zero-based element to seek from the head to
* the tail, negative indexes specify elements starting from the tail, where
* -1 means the last element, -2 the penultimate and so forth. If the index
* is out of range, NULL is returned. */
unsigned char *lpSeek(unsigned char *lp, long index) {
int forward = 1; /* Seek forward by default. */
/* We want to seek from left to right or the other way around
* depending on the listpack length and the element position.
* However if the listpack length cannot be obtained in constant time,
* we always seek from left to right. */
uint32_t numele = lpGetNumElements(lp);
if (numele != LP_HDR_NUMELE_UNKNOWN) {
if (index < 0) index = (long)numele+index;
if (index < 0) return NULL; /* Index still < 0 means out of range. */
if (index >= numele) return NULL; /* Out of range the other side. */
/* We want to scan right-to-left if the element we are looking for
* is past the half of the listpack. */
if (index > numele/2) {
forward = 0;
/* Left to right scanning always expects a negative index. Convert
* our index to negative form. */
index -= numele;
}
} else {
/* If the listpack length is unspecified, for negative indexes we
* want to always scan left-to-right. */
if (index < 0) forward = 0;
}
/* Forward and backward scanning is trivially based on lpNext()/lpPrev(). */
if (forward) {
unsigned char *ele = lpFirst(lp);
while (index > 0 && ele) {
ele = lpNext(lp,ele);
index--;
}
return ele;
} else {
unsigned char *ele = lpLast(lp);
while (index < -1 && ele) {
ele = lpPrev(lp,ele);
index++;
}
return ele;
}
}
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