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171 lines
3.9 KiB
C
171 lines
3.9 KiB
C
//
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// Created by longjin on 2022/1/22.
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//
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#include "printk.h"
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int skip_and_atoi(const char **s)
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{
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/**
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* @brief 获取连续的一段字符对应整数的值
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* @param:**s 指向 指向字符串的指针 的指针
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*/
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int ans = 0;
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while (is_digit(**s))
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{
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ans = ans * 10 + (**s) - '0';
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++(*s);
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}
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return ans;
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}
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int vsprintf(char *buf, const char *fmt, va_list args)
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{
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/**
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* 将字符串按照fmt和args中的内容进行格式化,然后保存到buf中
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* @param buf 结果缓冲区
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* @param fmt 格式化字符串
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* @param args 内容
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* @return 最终字符串的长度
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*/
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char *str, *s;
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str = buf;
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int flags; // 用来存储格式信息的bitmap
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int field_width; //区域宽度
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int precision; //精度
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int qualifier; //数据显示的类型
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int len;
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//开始解析字符串
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for (; *fmt; ++fmt)
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{
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//内容不涉及到格式化,直接输出
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if (*fmt != '%')
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{
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*str = *fmt;
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++str;
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}
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//开始格式化字符串
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//清空标志位和field宽度
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field_width = flags = 0;
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++fmt;
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bool flag_tmp = true;
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bool flag_break = false;
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while (flag_tmp)
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{
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switch (*fmt)
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{
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case '\0':
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//结束解析
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flag_break = true;
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flag_tmp = false;
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break;
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case '%':
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//输出 %
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*str = '%';
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++str;
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++fmt;
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flag_break = true;
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break;
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case '-':
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// 左对齐
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flags |= LEFT;
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++fmt;
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break;
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case '+':
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//在正数前面显示加号
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flags |= PLUS;
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++fmt;
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break;
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case ' ':
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flags |= SPACE;
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++fmt;
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break;
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case '#':
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//在八进制数前面显示 '0o',在十六进制数前面显示 '0x' 或 '0X'
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flags |= SPECIAL;
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++fmt;
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break;
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case '0':
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//显示的数字之前填充‘0’来取代空格
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flags |= PAD_ZERO;
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++fmt;
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break;
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default:
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flag_tmp = false;
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break;
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}
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}
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if (flag_break)
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break;
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//获取区域宽度
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if (*fmt == '*')
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{
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field_width = va_arg(args, int);
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++fmt;
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}
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else if (is_digit(*fmt))
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field_width = skip_and_atoi(&fmt);
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//获取小数精度
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if (*fmt == '.')
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{
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++fmt;
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if (*fmt == '*')
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{
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precision = va_arg(args, int);
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++fmt;
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}
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else if is_digit (*fmt)
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{
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precision = skip_and_atoi(&fmt);
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}
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}
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//获取要显示的数据的类型
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if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L' || *fmt == 'Z')
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{
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qualifier = *fmt;
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++fmt;
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}
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//转化成字符串
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switch (*fmt)
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{
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// 显示一个字符
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case 'c':
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//靠右对齐
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if (!(flags & LEFT))
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{
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while (--field_width)
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{
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*str = ' ';
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++str;
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}
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}
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else //靠左对齐
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{
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*str = (char)va_arg(args, int);
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++str;
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--field_width;
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}
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while (--field_width)
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{
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*str = ' ';
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++str;
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}
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break;
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default:
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break;
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}
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}
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} |