nginx中gzip_types匹配content-type的方式

gzip_type image/jpeg;

gzip_type "image/jpeg;charset:UTF-8";

static ngx_int_t
ngx_http_gzip_header_filter(ngx_http_request_t *r)
{
    ngx_table_elt_t       *h;
    ngx_http_gzip_ctx_t   *ctx;
    ngx_http_gzip_conf_t  *conf;

    conf = ngx_http_get_module_loc_conf(r, ngx_http_gzip_filter_module);

    if (!conf->enable
        || (r->headers_out.status != NGX_HTTP_OK
            && r->headers_out.status != NGX_HTTP_FORBIDDEN
            && r->headers_out.status != NGX_HTTP_NOT_FOUND)
        || (r->headers_out.content_encoding
            && r->headers_out.content_encoding->value.len)
        || (r->headers_out.content_length_n != -1
            && r->headers_out.content_length_n < conf->min_length)
            // ngx_http_test_content_type中对content_type做了校验
        || ngx_http_test_content_type(r, &conf->types) == NULL
        || r->header_only)
    {
        return ngx_http_next_header_filter(r);
    }
    ...
    }

void *
ngx_http_test_content_type(ngx_http_request_t *r, ngx_hash_t *types_hash)
{
    u_char      c, *lowcase;
    size_t      len;
    ngx_uint_t  i, hash;

    if (types_hash->size == 0) {
        return (void *) 4;
    }

    if (r->headers_out.content_type.len == 0) {
        return NULL;
    }

    len = r->headers_out.content_type_len;

    if (r->headers_out.content_type_lowcase == NULL) {

        lowcase = ngx_pnalloc(r->pool, len);
        if (lowcase == NULL) {
            return NULL;
        }

        r->headers_out.content_type_lowcase = lowcase;

        hash = 0;

        for (i = 0; i < len; i++) {
            c = ngx_tolower(r->headers_out.content_type.data[i]);
            hash = ngx_hash(hash, c);
            lowcase[i] = c;
        }

        r->headers_out.content_type_hash = hash;
    }

    return ngx_hash_find(types_hash, r->headers_out.content_type_hash,
                         r->headers_out.content_type_lowcase, len);
}

static ngx_int_t
ngx_http_set_content_type_header(ngx_http_request_t *r,
    ngx_http_lua_header_val_t *hv, ngx_str_t *value)
{
    ngx_uint_t          i;

	// 此时，r->headers_out.content_type_len与 value->len 还是相等的
    r->headers_out.content_type_len = value->len;


#if 1

    for (i = 0; i < value->len; i++) {
        if (value->data[i] == ';') {
        	// 找到第一个分号，然后修改了r->headers_out.content_type_len
            r->headers_out.content_type_len = i;
            break;
        }
    }
#endif

    r->headers_out.content_type = *value;
    r->headers_out.content_type_hash = hv->hash;
    r->headers_out.content_type_lowcase = NULL;

    value->len = 0;

    return ngx_http_set_header_helper(r, hv, value, NULL, 1);
}