[OTR-dev] otrl_base64_otr_decode() function...

[Justin Ferguson]

deja vu, (also looks like parse.c::decode() has the same construct):

gcry_error_t otrl_proto_data_read_flags(const char *datamsg,
	unsigned char *flagsp)
{
    char *otrtag, *endtag;
    unsigned char *rawmsg = NULL;
    unsigned char *bufp;
    size_t msglen, rawlen, lenp;
    unsigned char version;

    if (flagsp) *flagsp = 0;
    otrtag = strstr(datamsg, "?OTR:");
    if (!otrtag) {
	goto invval;
    }
    endtag = strchr(otrtag, '.');
    if (endtag) {
	msglen = endtag-otrtag;
    } else {
	msglen = strlen(otrtag);
    }

    /* Base64-decode the message */
    rawlen = ((msglen-5) / 4) * 3;   /* maximum possible */
    rawmsg = malloc(rawlen);
    if (!rawmsg && rawlen > 0) {
	return gcry_error(GPG_ERR_ENOMEM);
    }
    rawlen = otrl_base64_decode(rawmsg, otrtag+5, msglen-5);  /* actual size */


On Tue, Jul 17, 2012 at 2:56 PM, Ian Goldberg <ian at cypherpunks.ca> wrote:
> On Tue, Jul 17, 2012 at 10:39:39PM -0400, Paul Wouters wrote:
>> On Tue, 17 Jul 2012, Ian Goldberg wrote:
>>
>> >@@ -237,7 +237,7 @@ int otrl_base64_otr_decode(const char *msg, unsigned char **
>> >    }
>> >
>> >    /* Base64-decode the message */
>> >-    rawlen = ((msglen-5) / 4) * 3;   /* maximum possible */
>> >+    rawlen = ((msglen-5+3) / 4) * 3;   /* maximum possible */
>> >    rawmsg = malloc(rawlen);
>> >    if (!rawmsg && rawlen > 0) {
>> >       return -1;
>>
>> Personally, I prefer things like sizeof("===") over literals like '3'.
>
> The "3" is actually "4-1", as the way to write ceil(x/4) in C (with
> integer arithmetic) is (x+3)/4.
>
>    - Ian
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