void BN_CTX_start(BN_CTX *ctx)
{
CTXDBG_ENTRY("BN_CTX_start", ctx);
/* If we're already overflowing ... */
if (ctx->err_stack || ctx->too_many)
ctx->err_stack++;
/* (Try to) get a new frame pointer */
else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
BNerr(BN_F_BN_CTX_START, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
ctx->err_stack++;
}
CTXDBG_EXIT(ctx);
}
void BN_CTX_end(BN_CTX *ctx)
{
CTXDBG_ENTRY("BN_CTX_end", ctx);
if (ctx->err_stack)
ctx->err_stack--;
else {
unsigned int fp = BN_STACK_pop(&ctx->stack);
/* Does this stack frame have anything to release? */
if (fp < ctx->used)
BN_POOL_release(&ctx->pool, ctx->used - fp);
ctx->used = fp;
/* Unjam "too_many" in case "get" had failed */
ctx->too_many = 0;
}
CTXDBG_EXIT(ctx);
}
BIGNUM *BN_CTX_get(BN_CTX *ctx)
{
BIGNUM *ret;
CTXDBG_ENTRY("BN_CTX_get", ctx);
if(ctx->err_stack || ctx->too_many) return NULL;
if((ret = BN_POOL_get(&ctx->pool)) == NULL)
{
/* Setting too_many prevents repeated "get" attempts from
* cluttering the error stack. */
ctx->too_many = 1;
BNerr(BN_F_BN_CTX_GET,BN_R_TOO_MANY_TEMPORARY_VARIABLES);
return NULL;
}
/* OK, make sure the returned bignum is "zero" */
BN_zero(ret);
ctx->used++;
CTXDBG_RET(ctx, ret);
return ret;
}
