引言
前段时间接触到了跟abi（注意不是api）相关的知识，简单的了解了一下elf文件格式并写了两个小样例。
具体的步骤为：
- 修改readelf命令源码，增加其对h、S、l参数的json输出（修改后的代码过长就不放了）。
- 可以不修改json源码，我用linux平台下的json-c写了一个自己的样例。
- 对比获得的json文件，这里我用cJSON写了一个针对改后readelf的简单对比。
说实话对这方面兴趣真不大，发这篇博客当作一个因为个人原因可能即将烂尾的工程的纪念吧。
本篇博客代码和json文件下载：我的github仓库
elf文件格式简介：请参考《程序员的自我修养》第三章 目标文件里有什么
readelf命令简介：readelf (GNU Binary Utilities)
readelf命令源码：binutils/readelf.c
json文档：JSON中国 | JSON中文网
parse_elf_jsonc.c
#include <stdio.h>
#include <elf.h>
#include <fcntl.h>
#include <unistd.h>
#include <stddef.h>
#include "json-c/json.h"
#define my_err(format) { \
fprintf(stderr, "(File:%s, Line:%d) ", __FILE__, __LINE__); \
perror(format); \
exit(1); \
} \
void read_file_header(int fd, struct json_object *elf_json_object) {
if (lseek(fd, 0, SEEK_SET) == -1)
my_err("lseek error");
Elf64_Ehdr file_header;
if (read(fd, (void*)&file_header, sizeof(file_header)) == -1)
my_err("read error");
struct json_object *file_header_json_obeject = json_object_new_object();
unsigned char magic_string[17] = {
0};
for (int i = 0; i < 16; i++)
magic_string[i] = file_header.e_ident[i] + '0';
json_object_object_add(file_header_json_obeject, "Magic", json_object_new_string(magic_string));
json_object_object_add(file_header_json_obeject, "Type", json_object_new_int64(file_header.e_type));
json_object_object_add(file_header_json_obeject, "Machine", json_object_new_int64(file_header.e_machine));
json_object_object_add(file_header_json_obeject, "Version", json_object_new_int64(file_header.e_version));
json_object_object_add(file_header_json_obeject, "Entry point address", json_object_new_int64(file_header.e_entry));
json_object_object_add(file_header_json_obeject, "Start of program headers", json_object_new_int64(file_header.e_phoff));
json_object_object_add(file_header_json_obeject, "Start of section headers", json_object_new_int64(file_header.e_shoff));
json_object_object_add(file_header_json_obeject, "Flags", json_object_new_int64(file_header.e_flags));
json_object_object_add(file_header_json_obeject, "Size of this header", json_object_new_int64(file_header.e_ehsize));
json_object_object_add(file_header_json_obeject, "Size of program headers", json_object_new_int64(file_header.e_phentsize));
json_object_object_add(file_header_json_obeject, "Number of program headers", json_object_new_int64(file_header.e_phnum));
json_object_object_add(file_header_json_obeject, "Size of section header", json_object_new_int64(file_header.e_shentsize));
json_object_object_add(file_header_json_obeject, "Number of section headers", json_object_new_int64(file_header.e_shnum));
json_object_object_add(file_header_json_obeject, "Section header string table index", json_object_new_int64(file_header.e_shstrndx));
json_object_object_add(elf_json_object, "File Header", file_header_json_obeject);
}
void read_program_header(int fd, struct json_object *elf_json_object) {
if (lseek(fd, offsetof(Elf64_Ehdr, e_phoff), SEEK_SET) == -1)
my_err("lseek error");
Elf64_Off e_phoff;
if (read(fd, (void*)&e_phoff, sizeof(e_phoff)) == -1)
my_err("read error");
if (lseek(fd, offsetof(Elf64_Ehdr, e_phnum), SEEK_SET) == -1)
my_err("lseek error");
Elf64_Half e_phnum;
if (read(fd, (void*)&e_phnum, sizeof(e_phnum)) == -1)
my_err("read error");
if (lseek(fd, e_phoff, SEEK_SET) == -1)
my_err("lseek error");
Elf64_Phdr program_headers[e_phnum];
struct json_object *program_header_json_array = json_object_new_array();
for (Elf64_Half i = 0; i < e_phnum; i++) {
if (read(fd, (void *)&(program_headers[i]), sizeof(program_headers[i])) == -1)
my_err("read error");
struct json_object *program_header_json_array_i = json_object_new_object();
json_object_object_add(program_header_json_array_i, "Type", json_object_new_int64(program_headers[i].p_type));
json_object_object_add(program_header_json_array_i, "Offset", json_object_new_int64(program_headers[i].p_offset));
json_object_object_add(program_header_json_array_i, "VirtAddr", json_object_new_int64(program_headers[i].p_vaddr));
json_object_object_add(program_header_json_array_i, "PhysAddr", json_object_new_int64(program_headers[i].p_paddr));
json_object_object_add(program_header_json_array_i, "FileSiz", json_object_new_int64(program_headers[i].p_filesz));
json_object_object_add(program_header_json_array_i, "MemSiz", json_object_new_int64(program_headers[i].p_memsz));
json_object_object_add(program_header_json_array_i, "Flg", json_object_new_int64(program_headers[i].p_flags));
json_object_object_add(program_header_json_array_i, "Align", json_object_new_int64(program_headers[i].p_align));
json_object_array_add(program_header_json_array, program_header_json_array_i);
}
json_object_object_add(elf_json_object, "Program Headers", program_header_json_array);
}
void read_section_header(int fd, struct json_object *elf_json_object) {
if (lseek(fd, offsetof(Elf64_Ehdr, e_shoff), SEEK_SET) == -1)
my_err("lseek error");
Elf64_Off e_shoff;
if (read(fd, (void*)&e_shoff, sizeof(e_shoff)) == -1)
my_err("read error");
if (lseek(fd, offsetof(Elf64_Ehdr, e_shnum), SEEK_SET) == -1)
my_err("lseek error");
Elf64_Half e_shnum;
if (read(fd, (void*)&e_shnum, sizeof(e_shnum)) == -1)
my_err("read error");
if (lseek(fd, e_shoff, SEEK_SET) == -1)
my_err("lseek error");
Elf64_Shdr section_headers[e_shnum];
struct json_object *section_header_json_array = json_object_new_array();
for (Elf64_Half i = 0; i < e_shnum; i++) {
if (read(fd, (void *)&(section_headers[i]), sizeof(section_headers[i])) == -1)
my_err("read error");
struct json_object *section_header_json_array_i = json_object_new_object();
json_object_object_add(section_header_json_array_i, "Name", json_object_new_int64(section_headers[i].sh_name));
json_object_object_add(section_header_json_array_i, "Type", json_object_new_int64(section_headers[i].sh_type));
json_object_object_add(section_header_json_array_i, "Addr", json_object_new_int64(section_headers[i].sh_addr));
json_object_object_add(section_header_json_array_i, "Off", json_object_new_int64(section_headers[i].sh_offset));
json_object_object_add(section_header_json_array_i, "Size", json_object_new_int64(section_headers[i].sh_size));
json_object_object_add(section_header_json_array_i, "ES", json_object_new_int64(section_headers[i].sh_entsize));
json_object_object_add(section_header_json_array_i, "Flg", json_object_new_int64(section_headers[i].sh_flags));
json_object_object_add(section_header_json_array_i, "Lk", json_object_new_int64(section_headers[i].sh_link));
json_object_object_add(section_header_json_array_i, "Inf", json_object_new_int64(section_headers[i].sh_info));
json_object_object_add(section_header_json_array_i, "Al", json_object_new_int64(section_headers[i].sh_addralign));
json_object_array_add(section_header_json_array, section_header_json_array_i);
}
json_object_object_add(elf_json_object, "Program Headers", section_header_json_array);
}
int main(int argc, char **argv) {
if (argc != 2) {
printf("Usage : %s <filename>\n", argv[0]);
return -1;
}
int fd = open(argv[1], O_RDONLY);
// int fd = open("/home/nigo/桌面/try", O_RDONLY);
if (fd == -1)
my_err("open error");
struct json_object *elf_json_object = json_object_new_object();
read_file_header(fd, elf_json_object);
read_program_header(fd, elf_json_object);
read_section_header(fd, elf_json_object);
printf("%s\n", json_object_to_json_string(elf_json_object));
json_object_put(elf_json_object);
if (close(fd) == -1)
my_err("close error");
return 0;
}
compare_elf_cJSON.cpp
// c
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <cjson/cJSON.h>
#include <sys/stat.h>
#include <ctype.h>
#include <string.h>
#include <math.h>
// cpp
#include <map>
#include <vector>
#include <string>
#include <iostream>
#include <sstream>
using namespace std;
#define my_err(format) { \
fprintf(stderr, "(File:%s, Line:%d) ", __FILE__, __LINE__); \
perror(format); \
exit(1); \
} \
enum move_type {
move_none,
move_down,
move_right,
move_diagonal
};
map<move_type, const char*> color = {
{
move_down, "\033[32m"},
{
move_right, "\033[31m"},
{
move_diagonal, "\033[39m"},
{
move_none, "\033[0m"}
};
class Point {
friend move_type compare(const Point &prev_point, const Point &point);
public:
Point(int x, int y) {
this->x = x;
this->y = y;
}
bool operator==(const Point &point) const {
return this->x == point.x && this->y == point.y;
}
bool operator!=(const Point &point) const {
return this->x != point.x || this->y != point.y;
}
// move_type operator>(const Point &point) {
// if (this->x == point.x && this->y + 1 == point.y) {
// return move_down;
// } else if (this->y == point.y && this->x + 1 == point.x) {
// return move_right;
// } else if (this->x + 1 == point.x && this->y + 1 == point.y) {
// return move_diagonal;
// }
// return move_none;
// }
public:
int x = 0;
int y = 0;
};
// compare previous point and point
move_type compare(const Point &prev_point, const Point &point) {
if (prev_point.x == point.x && prev_point.y + 1 == point.y) {
return move_down;
} else if (prev_point.y == point.y && prev_point.x + 1 == point.x) {
return move_right;
} else if (prev_point.x + 1 == point.x && prev_point.y + 1 == point.y) {
return move_diagonal;
}
return move_none;
}
// myers' diff algorithm:
// T1 and T2 should overload operator[] and size
// for example, T1 and T2 can be
// string to compare character
// or vector<T> to compare T
template<typename T1, typename T2>
void myers_diff(const T1 &lhs, const T2 &rhs) {
int N = lhs.size();
int M = rhs.size();
// map to save v of every d
vector<map<int, int>> res_v;
// map to save x by k
// k -> x
map<int, int> v;
// base point : (0,-1)
v[1] = 0;
bool go_ahead = true;
// d: step(excludes move of diagonal)
// k: x - y
for (int d = 0; d <= N + M && go_ahead; d++) {
for (int k = -d; k <= d; k = k + 2) {
// delete is preferred
// so move right is preferred
// so bigger x is preferred
bool down = (k == -d || (k != d && v[k - 1] < v[k + 1]));
int k_prev = down ? k + 1 : k - 1;
// start point
int x_start = v[k_prev];
int y_start = x_start - k_prev;
// temp(mid) point
int x_tmp = down ? x_start : x_start + 1;
int y_tmp = x_tmp - k;
// end point
int x_end = x_tmp;
int y_end = y_tmp;
// move along the diagonal
while (x_end < N && y_end < M && lhs[x_end] == rhs[y_end]) {
++x_end;
++y_end;
}
v[k] = x_end;
// the result is found
if (x_end >= N && y_end >= M) {
go_ahead = false;
break;
}
}
// store the result
res_v.push_back(v);
}
// the fallback
vector<Point> path;
Point point(lhs.size(), rhs.size());
path.push_back(point);
for (int d = res_v.size() - 1; point.x > 0 || point.y > 0; --d) {
auto X = res_v[d];
int k = point.x - point.y;
int x_end = X[k];
int y_end = point.x - k;
// whether move along the diagonal
while (x_end > 0 && y_end > 0 && x_end <= N && y_end <= M && lhs[x_end - 1] == rhs[y_end - 1]) {
--x_end;
--y_end;
path.push_back(Point(x_end, y_end));
}
bool down = (k == -d || (k != d && X[k - 1] < X[k + 1]));
int k_prev = down ? k + 1 : k - 1;
int x_start = X[k_prev];
int y_start = x_start - k_prev;
path.push_back(Point(x_start, y_start));
point.x = x_start;
point.y = y_start;
}
// pop (0,-1)
path.pop_back();
// compare and print
if (path.size() >= 2) {
int size = path.size();
for (int i = size - 2; i >= 0; --i) {
Point prev_point = path[i + 1];
move_type type = compare(prev_point, path[i]);
switch (type) {
case move_right: {
cout << color[move_right] << "-" << lhs[prev_point.x] << endl;
break;
}
case move_down: {
cout << color[move_down] << "+" << rhs[prev_point.y] << endl;
break;
}
case move_diagonal: {
cout << color[move_diagonal] << "=" << lhs[prev_point.x] << endl;
break;
}
}
}
}
}
const int completed_option_nums = 2;
const double double_min_interval = 1e-6;
long int diff_item_num = 0, same_item_num = 0,
added_item_num = 0, deleted_item_num = 0;
// split std::string by sep
// then return a vector<string> to store the result
vector<string> split_string(const string &str, const string &sep) {
vector<string> res;
string temp_s = str + sep;
size_t pos = temp_s.find(sep);
size_t size = temp_s.size();
while (pos != string::npos) {
// escape empty string(when sep is in the end)
if (pos == 0)
break;
string s = temp_s.substr(0, pos);
res.push_back(s);
temp_s = temp_s.substr(pos + 1, size);
pos = temp_s.find(sep);
}
return res;
}
// parse from a filename to a json object
struct cJSON *cJSON_ParseFilename(const char *filename) {
int fd = open(filename, O_RDONLY);
if (fd == -1) my_err("open error");
// obtain file size
struct stat file_stat;
if (fstat(fd, &file_stat) == -1) my_err("fstat error");
__off_t size = file_stat.st_size;
// read file by size
char read_buf[size + 1];
read(fd, (void *)read_buf, size);
read_buf[size] = '\0';
if (close(fd) == -1) my_err("close error");
return cJSON_Parse(read_buf);
}
// judge buf whether is number key
int is_number_key(const char *buf) {
// number Key won't be printed
// atoi return 0 when error happens or string is "0"
if ((atoi(buf) != 0) && (!(*buf == '0' && (buf[1] == '\0'))))
return 0;
return 1;
}
// compare normal cJSON Object and print
int cJSON_ComparePrintNormal(const struct cJSON *object1, const struct cJSON *object2, const char *dst_str) {
const struct cJSON *json1, *json2;
json1 = cJSON_GetObjectItem(object1, dst_str);
json2 = cJSON_GetObjectItem(object2, dst_str);
// avoid null cJSON object
if ((!json1) || (!json2))
return -1;
// classify and compare
if (cJSON_IsString(json1) && cJSON_IsString(json2)) {
// for cJSON String Object
const char *str1, *str2;
str1 = cJSON_GetStringValue(json1);
str2 = cJSON_GetStringValue(json2);
if (strcmp(str1, str2) != 0) {
diff_item_num++;
if (is_number_key(dst_str))
printf("%s : \n", dst_str);
cout << color[move_right] << "-" << str1 << endl << color[move_none];
cout << color[move_down] << "+" << str2 << endl << color[move_none];
} else {
same_item_num++;
}
} else if (cJSON_IsNumber(json1) && cJSON_IsNumber(json2)) {
// for cJSON Number object
double d1, d2;
d1 = cJSON_GetNumberValue(json1);
d2 = cJSON_GetNumberValue(json2);
if (fabs(d1 - d2) > double_min_interval) {
diff_item_num++;
if (is_number_key(dst_str))
printf("%s : \n", dst_str);
printf("%s-%.0lf\n%s+%.0lf\n%s",
color[move_right], d1, color[move_down], d2, color[move_none]);
} else {
same_item_num++;
}
} else if (cJSON_IsObject(json1) && cJSON_IsObject(json2)) {
// for cJSON Object like "Version": {
// "0": 1,
// "1": "(current)"
// },
char nk_buf[11]; // number key buffer (0, 1, ...)
// INT_MAX is 2147483647
sprintf(nk_buf, "%d", 0);
while (cJSON_ComparePrintNormal(json1, json2, nk_buf) != -1) {
// 0 to 1 to ...
int nk = atoi(nk_buf);
sprintf(nk_buf, "%d", ++nk);
}
} else {
printf("%s\n", dst_str);
my_err("cJSON_ComparePrintNormal error");
}
return 0;
}
// compare option h then output
void compare_option_h(const char *filename1, const char *filename2) {
struct cJSON *object1 = cJSON_ParseFilename(filename1);
struct cJSON *object2 = cJSON_ParseFilename(filename2);
struct cJSON *temp1_cJSON, *temp2_cJSON;
temp1_cJSON = cJSON_GetObjectItem(object1, "ELF Header");
temp2_cJSON = cJSON_GetObjectItem(object2, "ELF Header");
printf("<option h> : \n");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "OS/ABI");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "ABI Version");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Type");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Machine");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Version");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Entry point address");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Start of program headers");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Start of section headers");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Size of this header");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Size of program headers");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Number of program headers");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Size of section headers");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Number of section headers");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Section header string table index");
// just delete root cJSON object
// otherwise cause double-free
cJSON_Delete(object1);
cJSON_Delete(object2);
}
// compare option S then output
void compare_option_S(const char *filename1, const char *filename2) {
struct cJSON *object1 = cJSON_ParseFilename(filename1);
struct cJSON *object2 = cJSON_ParseFilename(filename2);
struct cJSON *temp1_cJSON, *temp2_cJSON;
temp1_cJSON = cJSON_GetObjectItem(object1, "Section Headers");
temp2_cJSON = cJSON_GetObjectItem(object2, "Section Headers");
printf("<option S> \n");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "elf_header.e_shnum");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "elf_header.e_shoff");
// compare Section Headers
struct cJSON *temp1_array_cJSON, *temp2_array_cJSON;
temp1_array_cJSON = cJSON_GetObjectItem(temp1_cJSON, "Section Headers");
temp2_array_cJSON = cJSON_GetObjectItem(temp2_cJSON, "Section Headers");
printf("Section Headers : \n");
int array_size = cJSON_GetArraySize(temp1_array_cJSON);
if (array_size != cJSON_GetArraySize(temp2_array_cJSON)) my_err("cJSON_GetArraySize error");
for (int i = 0; i < array_size; ++i) {
temp1_cJSON = cJSON_GetArrayItem(temp1_array_cJSON, i);
temp2_cJSON = cJSON_GetArrayItem(temp2_array_cJSON, i);
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Name");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Type");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Off");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Size");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "ES");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Flg");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Lk");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Inf");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Al");
}
cJSON_Delete(object1);
cJSON_Delete(object2);
}
// compare option l then output
void compare_option_l(const char *filename1, const char *filename2) {
struct cJSON *object1 = cJSON_ParseFilename(filename1);
struct cJSON *object2 = cJSON_ParseFilename(filename2);
struct cJSON *temp1_cJSON, *temp2_cJSON;
temp1_cJSON = cJSON_GetObjectItem(object1, "Program Header");
temp2_cJSON = cJSON_GetObjectItem(object2, "Program Header");
printf("<option l> : \n");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Elf file type\"");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Entry point");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "elf_header.e_phnum");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "starting at offset");
// compare Section Headers
struct cJSON *temp1_array_cJSON, *temp2_array_cJSON;
temp1_array_cJSON = cJSON_GetObjectItem(temp1_cJSON, "Program Headers");
temp2_array_cJSON = cJSON_GetObjectItem(temp2_cJSON, "Program Headers");
printf("Program Headers : \n");
int array_size = cJSON_GetArraySize(temp1_array_cJSON);
if (array_size != cJSON_GetArraySize(temp2_array_cJSON)) my_err("cJSON_GetArraySize error");
for (int i = 0; i < array_size; ++i) {
temp1_cJSON = cJSON_GetArrayItem(temp1_array_cJSON, i);
temp2_cJSON = cJSON_GetArrayItem(temp2_array_cJSON, i);
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Type");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Offset");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "VirtAddr");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "PhysAddr");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "FileSiz");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "MemSiz");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Flg");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "Align");
}
cJSON_Delete(object1);
cJSON_Delete(object2);
}
// compare option r then output
void compare_option_r(const char *filename1, const char *filename2) {
struct cJSON *object1 = cJSON_ParseFilename(filename1);
struct cJSON *object2 = cJSON_ParseFilename(filename2);
struct cJSON *temp1_cJSON, *temp2_cJSON;
temp1_cJSON = cJSON_GetObjectItem(object1, "Relocation");
temp2_cJSON = cJSON_GetObjectItem(object2, "Relocation");
printf("<option r> : \n");
// compare .rel.dyn
struct cJSON *temp1_array_cJSON, *temp2_array_cJSON;
temp1_array_cJSON = cJSON_GetObjectItem(temp1_cJSON, ".rel.dyn");
temp2_array_cJSON = cJSON_GetObjectItem(temp2_cJSON, ".rel.dyn");
printf(".rel.dyn : \n");
int array_size = cJSON_GetArraySize(temp1_array_cJSON);
if (array_size != cJSON_GetArraySize(temp2_array_cJSON)) my_err("cJSON_GetArraySize error");
for (int i = 0; i < array_size; ++i) {
temp1_cJSON = cJSON_GetArrayItem(temp1_array_cJSON, i);
temp2_cJSON = cJSON_GetArrayItem(temp2_array_cJSON, i);
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "offset");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "info");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "type");
cJSON_ComparePrintNormal(temp1_cJSON, temp2_cJSON, "sym->value");
}
cJSON_Delete(object1);
cJSON_Delete(object2);
}
// print section cJSON object like
// {"section_name":{"0":"address","1":"value"}
void cJSON_PrintSection(struct cJSON *section_object, const char *section_name, move_type type) {
printf("%s", color[type]);
if (type == move_right) {
printf("-");
} else if (type == move_down) {
printf("+");
}
printf("%s : \n", section_name);
auto temp_cJSON = cJSON_GetObjectItem(section_object, section_name);
printf("address : %s\n", cJSON_GetObjectItem(temp_cJSON, "0")->valuestring);
auto vec_s = split_string(cJSON_GetObjectItem(temp_cJSON, "1")->valuestring, " ");
int i;
for (i = 0; i < vec_s.size(); i++) {
if (i == 4) {
i = 0;
printf("\n");
}
cout << vec_s[i] << " ";
}
if (i != 4)
printf("\n");
printf("%s", color[move_none]);
}
// compare section cJSON object like
// {"section_name":{"0":"address","1":"value"}
// return 0 when same, 1 when different
int cJSON_ComparePrintSection(const struct cJSON *object1, const struct cJSON *object2, const char *dst_str) {
int is_diff = 0;
int is_sname_print = 0;
const struct cJSON *json1, *json2;
json1 = cJSON_GetObjectItem(object1, dst_str);
json2 = cJSON_GetObjectItem(object2, dst_str);
auto temp1_cJSON = cJSON_GetObjectItem(json1, "0");
auto temp2_cJSON = cJSON_GetObjectItem(json2, "0");
auto temp1_str = cJSON_GetStringValue(temp1_cJSON);
auto temp2_str = cJSON_GetStringValue(temp2_cJSON);
if (strcmp(temp1_str, temp2_str)) {
is_diff = is_sname_print = 1;
printf("%s : \n", dst_str);
printf("address : \n");
printf("%s-%s\n%s",
color[move_right], temp1_str, color[move_none]);
printf("%s+%s\n%s",
color[move_down], temp2_str, color[move_none]);
}
temp1_cJSON = cJSON_GetObjectItem(json1, "1");
temp2_cJSON = cJSON_GetObjectItem(json2, "1");
temp1_str = cJSON_GetStringValue(temp1_cJSON);
temp2_str = cJSON_GetStringValue(temp2_cJSON);
if (strcmp(temp1_str, temp2_str)) {
if (!is_sname_print) {
is_sname_print = 1;
printf("%s : \n", dst_str);
}
printf("value : \n");
// myers' diff
myers_diff(split_string(temp1_str, " "), split_string(temp2_str, " "));
}
return is_diff;
}
// compare option x(improved) then output
// show all section headers
void compare_option_x_i(const char *filename1, const char *filename2) {
struct cJSON *object1 = cJSON_ParseFilename(filename1);
struct cJSON *object2 = cJSON_ParseFilename(filename2);
printf("<option x(improved)> : \n");
// compare Hex dump of section
struct cJSON *temp1_array_cJSON, *temp2_array_cJSON;
temp1_array_cJSON = cJSON_GetObjectItem(object1, "Hex dump of section");
temp2_array_cJSON = cJSON_GetObjectItem(object2, "Hex dump of section");
printf("Hex dump of section : \n");
int array1_size = cJSON_GetArraySize(temp1_array_cJSON);
int array2_size = cJSON_GetArraySize(temp2_array_cJSON);
struct cJSON *temp1_cJSON, *temp2_cJSON;
const char *section_name;
// the same string(const char*) may have different address
// so the key must be std::string
map<string, struct cJSON *> s_map;
// create a map of sections
for (int i = 0; i < array1_size; ++i) {
temp1_cJSON = cJSON_GetArrayItem(temp1_array_cJSON, i);
section_name = temp1_cJSON->child->string;
s_map[section_name] = temp1_cJSON;
}
// compare and update related variables
for (int i = 0; i < array2_size; ++i) {
temp2_cJSON = cJSON_GetArrayItem(temp2_array_cJSON, i);
section_name = temp2_cJSON->child->string;
if (s_map.find(section_name) != s_map.end()) {
// there are same sections in two file
// compare them
int is_diff = cJSON_ComparePrintSection(s_map[section_name], temp2_cJSON, section_name);
// after comparison, erase element
if (is_diff)
diff_item_num++;
else
same_item_num++;
s_map.erase(section_name);
} else {
// otherwise output individually
char *temp_str;
cJSON_PrintSection(temp2_cJSON, section_name, move_down);
added_item_num++;
}
}
// updating deleted_item_num must be here
deleted_item_num += s_map.size();
for (auto s : s_map) {
cJSON_PrintSection(s.second, s.first.c_str(), move_right);
// printf("%s-%s\n%s",
// color[move_right], cJSON_PrintUnformatted(s.second), color[move_none]);
}
cJSON_Delete(object1);
cJSON_Delete(object2);
}
int main(int argc, char *argv[]) {
// if (argc != completed_option_nums * 2 + 1) {
// printf("Usage : %s <filename-h-1> <filename-h-2> "
// "<filename-S-1> <filename-S-2> "
// "<filename-l-1> <filename-l-2> "
// "<filename-r-1> <filename-r-2> "
// "<filename-x-i-1> <filename-x-i-2> ", argv[0]);
// return -1;
// }
compare_option_h("h1.json", "h2.json");
compare_option_S("S1.json", "S2.json");
compare_option_l("l1.json", "l2.json");
compare_option_r("r1.json", "r2.json");
compare_option_x_i("x1.json", "x2.json");
// compare_option_h(argv[1], argv[2]);
// compare_option_S(argv[3], argv[4]);
// compare_option_l(argv[5], argv[6]);
// compare_option_r(argv[7], argv[8]);
// compare_option_x_i(argv[9], argv[10]);
printf("different items number : %d\n", diff_item_num);
printf("same items number : %d\n", same_item_num);
printf("added items number : %d\n", added_item_num);
printf("deleted items number : %d\n", deleted_item_num);
return 0;
}
由于一开始使用c去写这个东西，但是最后需要map的支持，为了方便我还是改成了cpp，代码风格比较乱。
这里涉及到一个让人头大的算法——Myers’ diff查分算法，我看了两天才看下来。
这个算法写出来其实挺有意思的，具体可以参考：
Git 是怎样生成 diff 的：Myers 算法 - CJ Ting’s Blog
一个Go的实现
具体论文地址