mirror of
https://github.com/facebook/sapling.git
synced 2024-10-07 23:38:50 +03:00
ab3a7cb21f
Summary: In preparation for merging fb-mercurial sources to the Eden repository, move everything from the top-level directory into an `eden/scm` subdirectory.
444 lines
14 KiB
C
444 lines
14 KiB
C
/*
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* Copyright 2016-present Facebook. All Rights Reserved.
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*
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* linelog.c: data structure tracking line changes
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*
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* This software may be used and distributed according to the terms of the
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* GNU General Public License version 2 or any later version.
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*/
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#include "linelog.h"
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#include <assert.h> /* assert */
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#include <stdbool.h> /* bool */
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#include <stdlib.h> /* realloc, free */
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#include <string.h> /* NULL, memcpy, memmove, memset */
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#if defined(_WIN32) || defined(_WIN64)
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/* Windows does not have arpa/inet.h. Reinvent htonl and ntohl. Modern x86
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* compiler could produce efficient "bswap" instruction. */
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#define bswap32(x) \
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{ \
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x = ((x << 8) & 0xFF00FF00) | ((x >> 8) & 0xFF00FF); \
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x = (x << 16) | (x >> 16); \
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}
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inline static int islittleendian(void) {
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uint32_t i = 1;
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return (*((uint8_t*)(&i))) == 1;
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}
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static uint32_t htonl(uint32_t x) {
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if (islittleendian())
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bswap32(x);
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return x;
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}
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#define ntohl htonl
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#else
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#include <arpa/inet.h> /* htonl, ntohl */
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#endif
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/* linelog_buf.data is a plain array of instructions.
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a linelog instruction has 8 bytes:
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opcode: 2 bits (linelog_opcode)
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operand1: 30 bits (linelog_revnum)
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operand2: 32 bits (linelog_offset | linelog_linenum)
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the first 8-byte slot is not a real instruction, but a 32-bit maxrev then
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a 32-bit instruction count indicating used buffer size. it can be parsed as
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a normal instruction to extract the information. the code usually uses
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"inst0" as the variable name for that purpose.
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real instructions start from the 9th byte. */
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typedef enum {
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JGE = 0, /* if rev >= operand1, jump to operand2 */
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JL = 1, /* if rev < operand1, jump to operand2 */
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LINE = 2, /* line introduced by rev = operand1, linenum = operand2 */
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} linelog_opcode;
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typedef struct {
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linelog_opcode opcode;
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linelog_revnum rev; /* uint32_t operand1 */
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linelog_offset offset; /* uint32_t operand2, linelog_linenum linenum */
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} linelog_inst;
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/* static assert uint32_t, linelog_{linenum,revnum,offset} have a same size */
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extern char linelog_assert_[1 / (sizeof(linelog_revnum) == sizeof(uint32_t))];
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extern char linelog_assert_[1 / (sizeof(linelog_linenum) == sizeof(uint32_t))];
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extern char linelog_assert_[1 / (sizeof(linelog_offset) == sizeof(uint32_t))];
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/* size of the encoded representation, not sizeof(linelog_inst) */
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#define INST_SIZE 8
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/* like linelog_{offset,linenum} but less likely to overflow */
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typedef size_t linelog_loffset;
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typedef size_t linelog_llinenum;
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/* hard limits, smaller than the physical limits to reserve some bits */
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#ifndef MIN
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#define MIN(x, y) (((x) < (y)) ? (x) : (y))
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#endif
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static const linelog_loffset MAX_OFFSET =
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MIN(0x0ffffff0u, SIZE_MAX / INST_SIZE);
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static const linelog_llinenum MAX_LINENUM =
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MIN(0x1ffffff0u, SIZE_MAX / sizeof(linelog_lineinfo));
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static const linelog_revnum MAX_REVNUM = 0x1ffffff0u;
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/* uint8_t[8] -> linelog_inst */
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static inline void decode(const uint8_t data[INST_SIZE], linelog_inst* inst) {
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uint32_t buf[2];
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memcpy(buf, data, sizeof(buf));
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buf[0] = ntohl(buf[0]);
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buf[1] = ntohl(buf[1]);
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inst->opcode = (linelog_opcode)(buf[0] & 3);
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inst->rev = (buf[0] >> 2) & 0x3fffffffu;
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inst->offset = buf[1];
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}
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/* uint8_t[8] <- linelog_inst */
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static inline void encode(uint8_t data[INST_SIZE], const linelog_inst* inst) {
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uint32_t buf[2];
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buf[0] = htonl((uint32_t)(inst->opcode) | (inst->rev << 2));
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buf[1] = htonl(inst->offset);
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memcpy(data, buf, sizeof(buf));
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}
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/* read instruction, with error checks */
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static inline linelog_result
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readinst(const linelog_buf* buf, linelog_inst* inst, linelog_loffset offset) {
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if (buf == NULL || buf->data == NULL || buf->size < INST_SIZE ||
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offset >= MAX_OFFSET)
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return LINELOG_RESULT_EILLDATA;
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size_t len = htonl(((const uint32_t*)buf->data)[1]);
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if (len > buf->size / INST_SIZE || offset >= len)
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return LINELOG_RESULT_EILLDATA;
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size_t offsetinbytes = (size_t)offset * INST_SIZE;
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decode(buf->data + offsetinbytes, inst);
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return LINELOG_RESULT_OK;
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}
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/* write instruction, with error checks */
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static inline linelog_result
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writeinst(linelog_buf* buf, const linelog_inst* inst, linelog_loffset offset) {
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if (offset >= MAX_OFFSET)
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return LINELOG_RESULT_EOVERFLOW;
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if (buf == NULL || (buf->data == NULL && buf->size > 0))
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return LINELOG_RESULT_EILLDATA;
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size_t offsetinbytes = (size_t)offset * INST_SIZE;
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if (offsetinbytes + INST_SIZE > buf->size) {
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buf->neededsize = offsetinbytes + INST_SIZE;
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return LINELOG_RESULT_ENEEDRESIZE;
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}
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encode(buf->data + offsetinbytes, inst);
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return LINELOG_RESULT_OK;
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}
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/* helper to make code shorter */
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#define returnonerror(expr) \
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{ \
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linelog_result result = (expr); \
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if (result != LINELOG_RESULT_OK) \
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return result; \
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}
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#define mustsuccess(expr) \
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{ \
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linelog_result result = (expr); \
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(void)result; /* eliminate "unused" warning with NDEBUG set */ \
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assert(result == LINELOG_RESULT_OK); \
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}
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/* ensure `ar->lines[0:linecount]` are valid */
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static linelog_result reservelines(
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linelog_annotateresult* ar,
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linelog_llinenum linecount) {
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if (linecount >= MAX_LINENUM)
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return LINELOG_RESULT_EOVERFLOW;
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if (ar->maxlinecount < linecount) {
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size_t size = sizeof(linelog_lineinfo) * linecount;
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void* p = realloc(ar->lines, size);
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if (p == NULL)
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return LINELOG_RESULT_ENOMEM;
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ar->lines = (linelog_lineinfo*)p;
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ar->maxlinecount = (linelog_linenum)linecount;
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}
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return LINELOG_RESULT_OK;
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}
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/* APIs declared in .h */
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void linelog_annotateresult_clear(linelog_annotateresult* ar) {
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free(ar->lines);
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memset(ar, 0, sizeof(linelog_annotateresult));
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}
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linelog_result linelog_clear(linelog_buf* buf) {
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linelog_inst insts[2] = {{JGE, 0, 2}, {JGE, 0, 0}};
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returnonerror(writeinst(buf, &insts[1], 1));
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returnonerror(writeinst(buf, &insts[0], 0));
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return LINELOG_RESULT_OK;
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}
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size_t linelog_getactualsize(const linelog_buf* buf) {
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linelog_inst inst0;
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linelog_result r = readinst(buf, &inst0, 0);
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if (r != LINELOG_RESULT_OK)
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return 0;
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return (size_t)(inst0.offset) * INST_SIZE;
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}
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linelog_revnum linelog_getmaxrev(const linelog_buf* buf) {
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linelog_inst inst0;
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linelog_result r = readinst(buf, &inst0, 0);
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if (r != LINELOG_RESULT_OK)
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return 0;
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return inst0.rev;
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}
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inline static linelog_result appendline(
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linelog_annotateresult* ar,
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const linelog_inst* inst,
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linelog_offset offset) {
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linelog_lineinfo info = {.rev = inst ? inst->rev : 0,
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.linenum = inst ? inst->offset /* linenum */ : 0,
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.offset = offset};
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returnonerror(reservelines(ar, ar->linecount + 1));
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ar->lines[ar->linecount++] = info;
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return LINELOG_RESULT_OK;
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}
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linelog_result linelog_annotate(
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const linelog_buf* buf,
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linelog_annotateresult* ar,
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linelog_revnum rev) {
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linelog_inst inst0;
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returnonerror(readinst(buf, &inst0, 0));
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linelog_offset pc, nextpc = 1, endoffset = 0;
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ar->linecount = 0;
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size_t step = (size_t)inst0.offset;
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while ((pc = nextpc++) != 0 && --step) {
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linelog_inst i;
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returnonerror(readinst(buf, &i, pc));
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switch (i.opcode) {
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case JGE:
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case JL: /* conditional jump */
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if (i.opcode == JGE ? rev >= i.rev : rev < i.rev) {
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nextpc = i.offset;
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if (nextpc == 0) /* met the END marker */
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endoffset = pc;
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}
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break;
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case LINE: /* append a line */
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returnonerror(appendline(ar, &i, pc));
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break;
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default: /* unknown opcode */
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return LINELOG_RESULT_EILLDATA;
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}
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}
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if (endoffset == 0) /* didn't meet a valid END marker */
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return LINELOG_RESULT_EILLDATA;
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/* ar->lines[ar->linecount].offset records the endoffset */
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returnonerror(appendline(ar, NULL, endoffset));
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ar->linecount--; /* do not include this special line */
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return LINELOG_RESULT_OK;
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}
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static linelog_result replacelines(
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linelog_buf* buf,
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linelog_annotateresult* ar,
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linelog_revnum brev,
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linelog_linenum a1,
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linelog_linenum a2,
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linelog_linenum b1,
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linelog_linenum b2,
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const linelog_revnum* brevs,
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const linelog_linenum* blinenums) {
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/* buf before after
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-------- --------
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.... ....
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a1addr > (a1inst) JGE 0 oldlen [5]
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a1addr+1 > ... ...
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.... ....
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a2addr > ... ...
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.... ....
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oldlen > (end) JL brev pjge [1]
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LINE brev b1 [1]
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LINE brev b1+1 [1]
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.... [1]
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LINE brev b2-1 [1]
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pjge > JGE brev a2addr [2]
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a1newaddr > (a1inst) [3]
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JGE 0 a1addr+1 [4]
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newlen > (end)
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[1]: insert new lines. only exist if b1 < b2
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[2]: delete old lines. only exist if a1 < a2
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[3]: move a1inst to new place, as it will be rewritten in [5]
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[4]: jump back. only exist if a1inst is not an unconditional jump
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[5]: rewrite the old instruction to jump to the new block */
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/* sanity check */
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linelog_inst inst0;
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returnonerror(readinst(buf, &inst0, 0));
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if (brev >= MAX_REVNUM || a2 >= MAX_LINENUM || b2 >= MAX_LINENUM)
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return LINELOG_RESULT_EOVERFLOW;
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if (a2 < a1 || b2 < b1 || !ar || a2 > ar->linecount || brev == 0 ||
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ar->linecount >= ar->maxlinecount)
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return LINELOG_RESULT_EILLDATA;
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/* useful variables for both step I and III */
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linelog_offset oldlen = inst0.offset;
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linelog_offset a1addr = ar->lines[a1].offset;
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linelog_inst a1inst;
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returnonerror(readinst(buf, &a1inst, a1addr));
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bool a1instisjge0 = (a1inst.opcode == JGE && a1inst.rev == 0);
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/* step I: reserve size for buf: (newlen - oldlen) more instructions */
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linelog_loffset newlen = (linelog_loffset)oldlen +
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(b2 - b1 /* LINE */ + (b2 > b1) /* JL brev */) /* [1] */
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+ (a2 > a1) /* JGE brev */ /* [2] */
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+ 1 /* a1inst */ /* [3] */
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+ (a1instisjge0 ? 0 : 1) /* JGE 0 */ /* [4] */;
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if (newlen >= MAX_OFFSET)
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return LINELOG_RESULT_EOVERFLOW;
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size_t neededsize = (size_t)newlen * INST_SIZE;
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if (neededsize > buf->size) {
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buf->neededsize = neededsize;
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return LINELOG_RESULT_ENEEDRESIZE;
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}
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/* step II: reserve space for annotateresult */
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linelog_llinenum newlinecount =
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(linelog_llinenum)ar->linecount + b2 - b1 - (a2 - a1);
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returnonerror(reservelines(ar, newlinecount + 1));
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assert(ar->linecount < ar->maxlinecount);
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/* writeinst should not fail for remaining steps - we have reserved
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enough space. any failure will be a huge headache for the caller. */
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/* step III: update linelog_buf */
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#define appendinst(inst) mustsuccess(writeinst(buf, &inst, inst0.offset++));
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if (b1 < b2) { /* [1] */
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linelog_offset pjge = oldlen + (b2 - b1 + 1);
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linelog_inst jl = {.opcode = JL, .rev = brev, .offset = pjge};
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appendinst(jl);
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for (linelog_linenum i = b1; i < b2; ++i) {
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linelog_inst lineinst = {
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.opcode = LINE,
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.rev = brevs ? brevs[i] : brev,
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.offset /* linenum */ = blinenums ? blinenums[i] : i};
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appendinst(lineinst);
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}
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}
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if (a1 < a2) { /* [2] */
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linelog_offset a2addr = ar->lines[a2].offset;
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/* delete a chunk of an old commit. be conservative, do not
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touch invisible lines between a2 - 1 and a2 */
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if (a2 > 0 && brev < inst0.rev /* maxrev */)
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a2addr = ar->lines[a2 - 1].offset + 1;
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linelog_inst jge = {.opcode = JGE, .rev = brev, .offset = a2addr};
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appendinst(jge);
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}
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linelog_offset a1newaddr = inst0.offset;
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appendinst(a1inst); /* [3] */
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if (!a1instisjge0) { /* [4] */
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linelog_inst ret = {/* .opcode = */ JGE,
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0,
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/* .offset = */ a1addr + 1};
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appendinst(ret);
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}
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#undef appendinst
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linelog_inst jge0 = {.opcode = JGE, .rev = 0, .offset = oldlen};
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mustsuccess(writeinst(buf, &jge0, a1addr)); /* [5] */
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/* step IV: write back updated inst0 */
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if (brev > inst0.rev)
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inst0.rev = brev;
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mustsuccess(writeinst(buf, &inst0, 0));
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/* step V: update annotateresult */
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ar->lines[a1].offset = a1newaddr; /* a1inst got moved */
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if (a2 - a1 != b2 - b1) {
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size_t movesize = sizeof(linelog_lineinfo) * (ar->linecount + 1 - a2);
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/* the memmove is safe as step II reserved the memory */
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memmove(ar->lines + a1 + b2 - b1, ar->lines + a2, movesize);
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ar->linecount = (linelog_linenum)newlinecount;
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}
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for (linelog_linenum i = b1; i < b2; ++i) {
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linelog_lineinfo* li = ar->lines + a1 + i - b1;
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li->rev = brevs ? brevs[i] : brev;
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li->linenum = blinenums ? blinenums[i] : i;
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li->offset = oldlen + i - b1 + 1;
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}
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return LINELOG_RESULT_OK;
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}
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linelog_result linelog_replacelines(
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linelog_buf* buf,
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linelog_annotateresult* ar,
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linelog_revnum brev,
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linelog_linenum a1,
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linelog_linenum a2,
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linelog_linenum b1,
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linelog_linenum b2) {
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return replacelines(buf, ar, brev, a1, a2, b1, b2, NULL, NULL);
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}
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linelog_result linelog_replacelines_vec(
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linelog_buf* buf,
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linelog_annotateresult* ar,
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linelog_revnum brev,
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linelog_linenum a1,
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linelog_linenum a2,
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linelog_linenum blinecount,
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const linelog_revnum* brevs,
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const linelog_linenum* blinenums) {
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return replacelines(buf, ar, brev, a1, a2, 0, blinecount, brevs, blinenums);
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}
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linelog_result linelog_getalllines(
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linelog_buf* buf,
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linelog_annotateresult* ar,
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linelog_offset offset1,
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linelog_offset offset2) {
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linelog_inst inst0;
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returnonerror(readinst(buf, &inst0, 0));
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linelog_offset pc, nextpc = offset1 ? offset1 : 1;
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ar->linecount = 0;
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for (linelog_offset step = inst0.offset; step; --step) {
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pc = nextpc++;
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if (pc == offset2 || pc == 0)
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return LINELOG_RESULT_OK;
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linelog_inst i;
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returnonerror(readinst(buf, &i, pc));
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switch (i.opcode) {
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case JGE:
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if (i.rev == 0) /* unconditional jump */
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nextpc = i.offset;
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break;
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case JL:
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break;
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case LINE: /* append a line */
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returnonerror(appendline(ar, &i, pc));
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break;
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default: /* unknown opcode */
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return LINELOG_RESULT_EILLDATA;
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}
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}
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/* step reaches 0, didn't meet the end condition */
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return LINELOG_RESULT_EILLDATA;
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}
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