NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/7831

Text File | 1996-08-05 | 1.9 KB | 55 lines

Path: anvil.ugrad.cs.ubc.ca!not-for-mail
From: [e-mail] (Kazimir Kylheku)
Newsgroups: comp.lang.c
Subject: Re: Generating pointer to struct from string
Date: 27 Feb 1996 12:45:49 -0800
Organization: Computer Science, University of B.C., Vancouver, B.C., Canada
Message-ID: <[e-mail]>
References: <4grk4g$[e-mail]>
NNTP-Posting-Host: anvil.ugrad.cs.ubc.ca

In article <4grk4g$[e-mail]>,
Vishram Dalvi <[e-mail]> wrote:
>Hello,
>
>Say I have 3 structs aaa, bbb and ccc of type foo:
>
>struct foo {
>    int flag;
>    char name[30]
>} aaa, bbb, ccc;
>
>I assign some values to the data members of all 3 structs. Now I prompt the
>user for the name of one of these structs. I read in the user entry into a
>char array. Assume that the user entered "aaa". How can I generate a pointer
>to the struct "aaa" from the user entry?
>I do not want a switch/case table (if user entered "aaa", access members of
>"aaa", if user entered "bbb"...).
>How do I cast a string into a struct address??
>Thanks in advance,

The names of C language objects are not accessible at run time. They are
temporary symbols needed to achieve a translation into the execution language.

This sort of thing is possible from debuggers, which have access to a symbol
table and other debugging information emitted by the compiler. In theory, you
could (in a very operating-system specific way) have a program search its own
debugging information (assuming it's available) and come up with a mapping for
a symbol name to an address.

The easiest way to do it is to just declare an array of strings whose names
match your structures, and search this array. You can sort it with qsort() and
then use bsearch(), if it is large.

Better yet, make each name a field of the structure, and put the structures
into an array:

struct foo {
    char name[8];
    int value;
} arr[] = { { "aaa" }, { "bbb" }, { "ccc" }};


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