字符串输入到Flex词法分析器 [英] String input to flex lexer

问题描述

我要创建使用Flex /野牛解析器读取-EVAL-打印循环。麻烦的是，弯曲产生的词法分析器想要的类型FILE *的投入，我想这是char *。反正有做到这一点？

I want to create a read-eval-print loop using flex/bison parser. Trouble is, the flex generated lexer wants input of type FILE* and i would like it to be char*. Is there anyway to do this?

一个建议是创建一个管道，喂它字符串和打开文件描述符和发送到词法分析器。这是相当简单的，但感觉费解的独立，而不是十分的平台。有没有更好的办法？

One suggestion has been to create a pipe, feed it the string and open the file descriptor and send to the lexer. This is fairly simple but it feels convoluted and not very platform independent. Is there a better way?

推荐答案

下面的函数可以用来扫描内存字符串而不是文件建立输入缓冲器（如yy_create_buffer一样）：

The following routines are available for setting up input buffers for scanning in-memory strings instead of files (as yy_create_buffer does):

• YY_BUFFER_STATE yy_scan_string（为const char * str中）：扫描NULL结尾的string`


• YY_BUFFER_STATE yy_scan_bytes（为const char *字节，INT LEN）：扫描len个字节（包括可能完全无效）起始地址字节

• YY_BUFFER_STATE yy_scan_string(const char *str): scans a NUL-terminated string`
• YY_BUFFER_STATE yy_scan_bytes(const char *bytes, int len): scans len bytes (including possibly NULs) starting at location bytes

请注意，这两个函数创建，返回相应YY_BUFFER_STATE手柄（你必须yy_delete_buffer删除（）时，用它做），这样函数yylex（）扫描字符串或字节的副本。此行为可能是希望的，因为函数yylex（）修改缓冲区是扫描）的内容。

Note that both of these functions create, return a corresponding YY_BUFFER_STATE handle (which you must delete with yy_delete_buffer() when done with it) so yylex() scan a copy of the string or bytes. This behavior may be desirable since yylex() modifies the contents of the buffer it is scanning).

如果你想使用避免复制（和yy_delete_buffer）：

If you want avoid the copy (and yy_delete_buffer) using:

• YY_BUFFER_STATE yy_scan_buffer（字符*基地，yy_size_t大小）

• YY_BUFFER_STATE yy_scan_buffer(char *base, yy_size_t size)

样本主：

int main() {
    yy_scan_buffer("a test string");
    yylex();
}

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