prefix.c

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/*
 * BinReloc - a library for creating relocatable executables
 * Written by: Mike Hearn <mike@theoretic.com>
 *             Hongli Lai <h.lai@chello.nl>
 * http://autopackage.org/
 *
 * This source code is public domain. You can relicense this code
 * under whatever license you want.
 *
 * NOTE: if you're using C++ and are getting "undefined reference
 * to br_*", try renaming prefix.c to prefix.cpp
 */
 
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
 
/*
 * enrico - all the code below is only compiled and used if ENABLE_BINRELOC is set in config.h,
 *          this only happens if configure option --enable-binreloc was used
 */
#ifdef ENABLE_BINRELOC
 
 
 
#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
#include <string.h>
#include <glib.h>
#include "prefix.h"
 
 
#undef NULL
#define NULL ((void *) 0)
 
#ifdef __GNUC__
    #define br_return_val_if_fail(expr,val) if (!(expr)) {fprintf (stderr, "** BinReloc (%s): assertion %s failed\n", __PRETTY_FUNCTION__, #expr); return val;}
#else
    #define br_return_val_if_fail(expr, val) if (!(expr)) return val
#endif /* __GNUC__ */
 
 
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/param.h>
#include <unistd.h>
 
 
static char *br_last_value = (char*)NULL;
 
 
static void
br_free_last_value (void)
{
    if (br_last_value)
        free (br_last_value);
}
 
 
/**
 * br_thread_local_store:
 * str: A dynamically allocated string.
 * Returns: str. This return value must not be freed.
 *
 * Store str in a thread-local variable and return str. The next
 * you run this function, that variable is freed too.
 * This function is created so you don't have to worry about freeing
 * strings.
 *
 * Example:
 * char *foo;
 * foo = thread_local_store (strdup ("hello")); --> foo == "hello"
 * foo = thread_local_store (strdup ("world")); --> foo == "world"; "hello" is now freed.
 */
const char *
br_thread_local_store (char *str)
{
    static int initialized = 0;
 
 
    if (!initialized)
    {
        atexit (br_free_last_value);
        initialized = 1;
    }
 
    if (br_last_value)
        free (br_last_value);
    br_last_value = str;
 
    return (const char *) str;
}
 
 
/**
 * br_locate:
 * symbol: A symbol that belongs to the app/library you want to locate.
 * Returns: A newly allocated string containing the full path of the
 *      app/library that func belongs to, or NULL on error. This
 *      string should be freed when not when no longer needed.
 *
 * Finds out to which application or library symbol belongs, then locate
 * the full path of that application or library.
 * Note that symbol cannot be a pointer to a function. That will not work.
 *
 * Example:
 * --> main.c
 * #include "prefix.h"
 * #include "libfoo.h"
 *
 * int main (int argc, char *argv[]) {
 *  printf ("Full path of this app: %s\n", br_locate (&argc));
 *  libfoo_start ();
 *  return 0;
 * }
 *
 * --> libfoo.c starts here
 * #include "prefix.h"
 *
 * void libfoo_start () {
 *  --> "" is a symbol that belongs to libfoo (because it's called
 *  --> from libfoo_start()); that's why this works.
 *  printf ("libfoo is located in: %s\n", br_locate (""));
 * }
 */
char *
br_locate (void *symbol)
{
    char line[5000];
    FILE *f;
    char *path;
 
    br_return_val_if_fail (symbol != NULL, NULL);
 
    f = fopen ("/proc/self/maps", "r");
    if (!f)
        return NULL;
 
    while (!feof (f))
    {
        unsigned long start, end;
 
        if (!fgets (line, sizeof (line), f))
            continue;
        if (!strstr (line, " r-xp ") || !strchr (line, '/'))
            continue;
 
        sscanf (line, "%lx-%lx ", &start, &end);
        if (symbol >= (void *) start && symbol < (void *) end)
        {
            char *tmp;
            gsize len;
 
            /* Extract the filename; it is always an absolute path */
            path = strchr (line, '/');
 
            /* Get rid of the newline */
            tmp = strrchr (path, '\n');
            if (tmp) *tmp = 0;
 
            /* Get rid of "(deleted)" */
            len = strlen (path);
            if (len > 10 && strcmp (path + len - 10, " (deleted)") == 0)
            {
                tmp = path + len - 10;
                *tmp = 0;
            }
 
            fclose(f);
            return strdup (path);
        }
    }
 
    fclose (f);
    return NULL;
}
 
 
/**
 * br_extract_prefix:
 * path: The full path of an executable or library.
 * Returns: The prefix, or NULL on error. This string should be freed when no longer needed.
 *
 * Extracts the prefix from path. This function assumes that your executable
 * or library is installed in an LSB-compatible directory structure.
 *
 * Example:
 * br_extract_prefix ("/usr/bin/gnome-panel");       --> Returns "/usr"
 * br_extract_prefix ("/usr/local/lib/libfoo.so");   --> Returns "/usr/local"
 * br_extract_prefix ("/usr/local/libfoo.so");       --> Returns "/usr"
 */
char *
br_extract_prefix (const char *path)
{
    char *end, *tmp, *result;
 
    br_return_val_if_fail (path != (char*)NULL, (char*)NULL);
 
    if (!*path) return strdup ("/");
    end = strrchr (path, '/');
    if (!end) return strdup (path);
 
    tmp = g_strndup ((char *) path, end - path);
    if (!*tmp)
    {
        g_free (tmp);
        return strdup ("/");
    }
    end = strrchr (tmp, '/');
    if (!end) return tmp;
 
    result = g_strndup (tmp, end - tmp);
    g_free (tmp);
 
    if (!*result)
    {
        g_free (result);
        result = strdup ("/");
    }
 
    return result;
}
 
 
/**
 * br_locate_prefix:
 * symbol: A symbol that belongs to the app/library you want to locate.
 * Returns: A prefix. This string should be freed when no longer needed.
 *
 * Locates the full path of the app/library that symbol belongs to, and return
 * the prefix of that path, or NULL on error.
 * Note that symbol cannot be a pointer to a function. That will not work.
 *
 * Example:
 * --> This application is located in /usr/bin/foo
 * br_locate_prefix (&argc);   --> returns: "/usr"
 */
char *
br_locate_prefix (void *symbol)
{
    char *path, *prefix;
 
    br_return_val_if_fail (symbol != NULL, NULL);
 
    path = br_locate (symbol);
    if (!path) return NULL;
 
    prefix = br_extract_prefix (path);
    free (path);
    return prefix;
}
 
 
/**
 * br_prepend_prefix:
 * symbol: A symbol that belongs to the app/library you want to locate.
 * path: The path that you want to prepend the prefix to.
 * Returns: The new path, or NULL on error. This string should be freed when no
 *      longer needed.
 *
 * Gets the prefix of the app/library that symbol belongs to. Prepend that prefix to path.
 * Note that symbol cannot be a pointer to a function. That will not work.
 *
 * Example:
 * --> The application is /usr/bin/foo
 * br_prepend_prefix (&argc, "/share/foo/data.png");   --> Returns "/usr/share/foo/data.png"
 */
char *
br_prepend_prefix (void *symbol, char *path)
{
    char *tmp, *newpath;
 
    br_return_val_if_fail (symbol != NULL, NULL);
    br_return_val_if_fail (path != NULL, NULL);
 
    tmp = br_locate_prefix (symbol);
    if (!tmp) return NULL;
 
    if (strcmp (tmp, "/") == 0)
        newpath = strdup (path);
    else
        newpath = g_strconcat (tmp, path, NULL);
 
    free (tmp);
    return newpath;
}
 
 
#else /* ENABLE_BINRELOC */
 
typedef int iso_c_forbids_an_empty_source_file;
 
#endif /* ENABLE_BINRELOC */