grub/kern/env.c
2010-01-20 09:12:47 +01:00

429 lines
8.7 KiB
C

/* env.c - Environment variables */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2003,2005,2006,2007,2008,2009 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/env.h>
#include <grub/misc.h>
#include <grub/mm.h>
/* The size of the hash table. */
#define HASHSZ 13
/* A hashtable for quick lookup of variables. */
struct grub_env_context
{
/* A hash table for variables. */
struct grub_env_var *vars[HASHSZ];
/* One level deeper on the stack. */
struct grub_env_context *prev;
};
/* This is used for sorting only. */
struct grub_env_sorted_var
{
struct grub_env_var *var;
struct grub_env_sorted_var *next;
};
/* The initial context. */
static struct grub_env_context initial_context;
/* The current context. */
static struct grub_env_context *current_context = &initial_context;
/* Return the hash representation of the string S. */
static unsigned int
grub_env_hashval (const char *s)
{
unsigned int i = 0;
/* XXX: This can be done much more efficiently. */
while (*s)
i += 5 * *(s++);
return i % HASHSZ;
}
static struct grub_env_var *
grub_env_find (const char *name)
{
struct grub_env_var *var;
int idx = grub_env_hashval (name);
/* Look for the variable in the current context. */
for (var = current_context->vars[idx]; var; var = var->next)
if (grub_strcmp (var->name, name) == 0)
return var;
return 0;
}
grub_err_t
grub_env_context_open (int export)
{
struct grub_env_context *context;
int i;
context = grub_zalloc (sizeof (*context));
if (! context)
return grub_errno;
context->prev = current_context;
current_context = context;
/* Copy exported variables. */
for (i = 0; i < HASHSZ; i++)
{
struct grub_env_var *var;
for (var = context->prev->vars[i]; var; var = var->next)
{
if (export && var->type == GRUB_ENV_VAR_GLOBAL)
{
if (grub_env_set (var->name, var->value) != GRUB_ERR_NONE)
{
grub_env_context_close ();
return grub_errno;
}
grub_env_export (var->name);
grub_register_variable_hook (var->name, var->read_hook, var->write_hook);
}
}
}
return GRUB_ERR_NONE;
}
grub_err_t
grub_env_context_close (void)
{
struct grub_env_context *context;
int i;
if (! current_context->prev)
grub_fatal ("cannot close the initial context");
/* Free the variables associated with this context. */
for (i = 0; i < HASHSZ; i++)
{
struct grub_env_var *p, *q;
for (p = current_context->vars[i]; p; p = q)
{
q = p->next;
grub_free (p->name);
if (p->type != GRUB_ENV_VAR_DATA)
grub_free (p->value);
grub_free (p);
}
}
/* Restore the previous context. */
context = current_context->prev;
grub_free (current_context);
current_context = context;
return GRUB_ERR_NONE;
}
static void
grub_env_insert (struct grub_env_context *context,
struct grub_env_var *var)
{
int idx = grub_env_hashval (var->name);
/* Insert the variable into the hashtable. */
var->prevp = &context->vars[idx];
var->next = context->vars[idx];
if (var->next)
var->next->prevp = &(var->next);
context->vars[idx] = var;
}
static void
grub_env_remove (struct grub_env_var *var)
{
/* Remove the entry from the variable table. */
*var->prevp = var->next;
if (var->next)
var->next->prevp = var->prevp;
}
grub_err_t
grub_env_export (const char *name)
{
struct grub_env_var *var;
var = grub_env_find (name);
if (! var)
{
grub_err_t err;
err = grub_env_set (name, "");
if (err)
return err;
var = grub_env_find (name);
}
var->type = GRUB_ENV_VAR_GLOBAL;
return GRUB_ERR_NONE;
}
grub_err_t
grub_env_set (const char *name, const char *val)
{
struct grub_env_var *var;
/* If the variable does already exist, just update the variable. */
var = grub_env_find (name);
if (var)
{
char *old = var->value;
if (var->write_hook)
var->value = var->write_hook (var, val);
else
var->value = grub_strdup (val);
if (! var->value)
{
var->value = old;
return grub_errno;
}
grub_free (old);
return GRUB_ERR_NONE;
}
/* The variable does not exist, so create a new one. */
var = grub_zalloc (sizeof (*var));
if (! var)
return grub_errno;
/* This is not necessary, because GRUB_ENV_VAR_LOCAL == 0. But leave
this for readability. */
var->type = GRUB_ENV_VAR_LOCAL;
var->name = grub_strdup (name);
if (! var->name)
goto fail;
var->value = grub_strdup (val);
if (! var->value)
goto fail;
grub_env_insert (current_context, var);
return GRUB_ERR_NONE;
fail:
grub_free (var->name);
grub_free (var->value);
grub_free (var);
return grub_errno;
}
char *
grub_env_get (const char *name)
{
struct grub_env_var *var;
var = grub_env_find (name);
if (! var)
return 0;
if (var->read_hook)
return var->read_hook (var, var->value);
return var->value;
}
void
grub_env_unset (const char *name)
{
struct grub_env_var *var;
var = grub_env_find (name);
if (! var)
return;
if (var->read_hook || var->write_hook)
{
grub_env_set (name, "");
return;
}
grub_env_remove (var);
grub_free (var->name);
if (var->type != GRUB_ENV_VAR_DATA)
grub_free (var->value);
grub_free (var);
}
void
grub_env_iterate (int (*func) (struct grub_env_var *var))
{
struct grub_env_sorted_var *sorted_list = 0;
struct grub_env_sorted_var *sorted_var;
int i;
/* Add variables associated with this context into a sorted list. */
for (i = 0; i < HASHSZ; i++)
{
struct grub_env_var *var;
for (var = current_context->vars[i]; var; var = var->next)
{
struct grub_env_sorted_var *p, **q;
/* Ignore data slots. */
if (var->type == GRUB_ENV_VAR_DATA)
continue;
sorted_var = grub_malloc (sizeof (*sorted_var));
if (! sorted_var)
goto fail;
sorted_var->var = var;
for (q = &sorted_list, p = *q; p; q = &((*q)->next), p = *q)
{
if (grub_strcmp (p->var->name, var->name) > 0)
break;
}
sorted_var->next = *q;
*q = sorted_var;
}
}
/* Iterate FUNC on the sorted list. */
for (sorted_var = sorted_list; sorted_var; sorted_var = sorted_var->next)
if (func (sorted_var->var))
break;
fail:
/* Free the sorted list. */
for (sorted_var = sorted_list; sorted_var; )
{
struct grub_env_sorted_var *tmp = sorted_var->next;
grub_free (sorted_var);
sorted_var = tmp;
}
}
grub_err_t
grub_register_variable_hook (const char *name,
grub_env_read_hook_t read_hook,
grub_env_write_hook_t write_hook)
{
struct grub_env_var *var = grub_env_find (name);
if (! var)
{
if (grub_env_set (name, "") != GRUB_ERR_NONE)
return grub_errno;
var = grub_env_find (name);
/* XXX Insert an assertion? */
}
var->read_hook = read_hook;
var->write_hook = write_hook;
return GRUB_ERR_NONE;
}
static char *
mangle_data_slot_name (const char *name)
{
return grub_xasprintf ("\e%s", name);
}
grub_err_t
grub_env_set_data_slot (const char *name, const void *ptr)
{
char *mangled_name;
struct grub_env_var *var;
mangled_name = mangle_data_slot_name (name);
if (! mangled_name)
goto fail;
/* If the variable does already exist, just update the variable. */
var = grub_env_find (mangled_name);
if (var)
{
var->value = (char *) ptr;
return GRUB_ERR_NONE;
}
/* The variable does not exist, so create a new one. */
var = grub_zalloc (sizeof (*var));
if (! var)
goto fail;
var->type = GRUB_ENV_VAR_DATA;
var->name = mangled_name;
var->value = (char *) ptr;
grub_env_insert (current_context, var);
return GRUB_ERR_NONE;
fail:
grub_free (mangled_name);
return grub_errno;
}
void *
grub_env_get_data_slot (const char *name)
{
char *mangled_name;
void *ptr = 0;
mangled_name = mangle_data_slot_name (name);
if (! mangled_name)
goto fail;
ptr = grub_env_get (mangled_name);
grub_free (mangled_name);
fail:
return ptr;
}
void
grub_env_unset_data_slot (const char *name)
{
char *mangled_name;
mangled_name = mangle_data_slot_name (name);
if (! mangled_name)
return;
grub_env_unset (mangled_name);
grub_free (mangled_name);
}