int url_open(URLContext **puc, const char *filename, int flags)
{
URLContext *uc;
URLProtocol *up;
const char *p;
char proto_str[128], *q;
int err;
p = filename;
q = proto_str;
while (*p != '\0' && *p != ':') {
/* protocols can only contain alphabetic chars */
if (!isalpha(*p))
goto file_proto;
if ((q - proto_str) < sizeof(proto_str) - 1)
*q++ = *p;
p++;
}
/* if the protocol has length 1, we consider it is a dos drive */
if (*p == '\0' || (q - proto_str) <= 1) {
file_proto:
strcpy(proto_str, "file");
} else {
*q = '\0';
}
up = first_protocol;
while (up != NULL) {
if (!strcmp(proto_str, up->name))
goto found;
up = up->next;
}
err = AVERROR(ENOENT);
goto fail;
found:
uc = av_malloc(sizeof(URLContext) + strlen(filename) + 1);
if (!uc) {
err = AVERROR(ENOMEM);
goto fail;
}
#if LIBAVFORMAT_VERSION_INT >= (52<<16)
uc->filename = (char *) &uc[1];
#endif
strcpy(uc->filename, filename);
uc->prot = up;
uc->flags = flags;
uc->is_streamed = 0; /* default = not streamed */
uc->max_packet_size = 0; /* default: stream file */
err = up->url_open(uc, filename, flags);
if (err < 0) {
av_free(uc);
*puc = NULL;
return err;
}
*puc = uc;
return 0;
fail:
*puc = NULL;
return err;
}
int url_open(URLContext **puc, const char *filename, int flags)
{
URLContext *uc;
URLProtocol *up;
const char *p;
char proto_str[128], *q;
int err;
p = filename;
q = proto_str;
while (*p != '\0' && *p != ':')
{
if (!isalpha(*p)) // protocols can only contain alphabetic chars 协议头中包含特殊字符就是文件类型
goto file_proto;
if ((q - proto_str) < sizeof(proto_str) - 1)
*q++ = *p; //协议名放入proto_str
p++;
}
// if the protocol has length 1, we consider it is a dos drive
if (*p == '\0' || (q - proto_str) <= 1)
{
file_proto:
strcpy(proto_str, "file");
}
else
{
*q = '\0';
}
up = first_protocol;
while (up != NULL)
{
if (!strcmp(proto_str, up->name))
goto found; //找到后跳转
up = up->next;
}
err = - ENOENT;
goto fail;
found:
uc = av_malloc(sizeof(URLContext) + strlen(filename));
if (!uc)
{
err = - ENOMEM;
goto fail;
}
strcpy(uc->filename, filename); //strcpy拷贝的时候是包含最后一个'\0'的
uc->prot = up; //具体的源文件协议
uc->flags = flags;
uc->max_packet_size = 0; // default: stream file
err = up->url_open(uc, filename, flags);
if (err < 0)
{
av_free(uc);
*puc = NULL;
return err;
}
*puc = uc;
return 0;
fail:
*puc = NULL;
return err;
}
