Re: LexerInput

[Mihai Badea]

Mihai Badea wrote:
> Mihai Badea wrote:
> > Hi,
> >
> > I am studying a way to parse text data directly from memory (without 
> > using aditional temporary buffers). My questions are:
> > For C Flex:
> > What is the procedure to make sure that after using scan_buffer() as 
> > input method for Flex, the directly-scanned memory buffer remains 
> > intact (the content is restored)?
> > For Flex++:
> > Is there a way to addapt LexerInput() in such a way the scanning is 
> > done directly from the memory instead of reading into an additional 
> > buffer? If so, I have the same question regarding to the preservation 
> > of the buffer.
> > Any information or link to something would be helpful.
> >
> > Thanks and best regards,
> > Mihai
>
> Well seems to me that either my question was not well stated, or maybe 
> it was not a problem of any interest or I don't know...
> Please someone reply to me (even in pvt) and say anything (stupid 
> question etc.).


Hi Martin,

Thanks for your answer:

>   Did you try it, and it corrupted your buffer?  Since flex can read
> input from a read-only file or stream, it's not even supposed to be
> possible to alter the input...
>
> - - Martin Thurn

Regarding this, maybe I haven't well stated my question. Flex uses an 
internal buffer to process text data:

------------------------------------------------
|Original Input Data (File/Stream/Memory) (R/O)|
------------------------------------------------
        |
        |
        V
----------------------------------------------
|Flex's Internal Buffer (R/W) (gets modified)|
----------------------------------------------
        |
        |
        V
--------------------------------------
|Desired Results (i.e. data stucture)|
--------------------------------------

As I already have the text in memory, I try to avoid the internal buffer 
(by using directly the original buffer):

--------------------------------------------------
--------------------------------------------------
|| Original Data && Flex's Internal buffer (R/W)||
--------------------------------------------------
--------------------------------------------------
        |
        |
        V
--------------------------------------
|Desired Results (i.e. data stucture)|
--------------------------------------

Although possible, this will modify the original data buffer. What I was 
trying to find was a safe mechanism to ensure the integrity of the 
original buffer at the end of the scanning.

Best regards,
Mihai