NGINX(七)分段下載
前言
nginx分段下載經過ngx_http_range_filter_module模塊進行處理，關於HTTP分段下載過程，能夠參考HTTP分段下載一文，主要分爲一次請求一段和一次請求多段nginx
涉及數據結構
typedef struct {
/*文件開始位置*/
off_t start ;
/*文件結束位置*/
off_t end ;
/*一次請求多個部分時Content-Range字段 格式：SSSS-EEEE/TTTT*/
ngx_str_t content_range ;
} ngx_http_range_t;
typedef struct {
/*偏移量*/
off_t offset ;
/*一次請求多個部分時內容中分割內容包含boundary(分割符), Content-Type, Content-Range三個字段*/
ngx_str_t boundary_header ;
/*ngx_http_range_t數組*/
ngx_array_t ranges ;
} ngx_http_range_filter_ctx_t;
內容進行分段
入口函數ngx_http_range_header_filter，首先判斷請求中If-Range字段是否存在，If-Range字段格式 If-Range:"Etag" 或者 If-Range:modify_time，If-Range中保存文件Etag
值或者文件修改時間，若是判斷Etag值和當前輸出的文件值一致或者文件modify_time與If—Range中時間一致，則只返回請求的Range內容，不然返回文件全部內容。nginx判斷If-Range最後一個字節若是是雙引號則內容爲etag，反之則是修改時間，代碼以下。數組
static ngx_int_t
ngx_http_range_header_filter(ngx_http_request_t *r)
{
time_t if_range_time;
ngx_str_t *if_range, *etag;
ngx_uint_t ranges;
ngx_http_core_loc_conf_t *clcf;
ngx_http_range_filter_ctx_t *ctx;
if (r->http_version < NGX_HTTP_VERSION_10
|| r->headers_out.status != NGX_HTTP_OK
|| r != r->main
|| r->headers_out.content_length_n == -1
|| !r->allow_ranges)
{
return ngx_http_next_header_filter(r);
}
clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
if (clcf->max_ranges == 0) {
return ngx_http_next_header_filter(r);
}
if (r->headers_in.range == NULL
|| r->headers_in.range->value.len < 7
|| ngx_strncasecmp(r->headers_in.range->value.data,
(u_char *) "bytes=", 6)
!= 0)
{
goto next_filter;
}
/*頭部存在If-Range字段*/
if (r->headers_in.if_range) {
if_range = &r->headers_in.if_range->value;
/*判斷是不是etag*/
if (if_range->len >= 2 && if_range->data[if_range->len - 1] == '"') {
if (r->headers_out.etag == NULL) {
goto next_filter;
}
etag = &r->headers_out.etag->value;
/*與輸出的etag比較，一致則返回Range內容，不然返回全部內容*/
if (if_range->len != etag->len
|| ngx_strncmp(if_range->data, etag->data, etag->len) != 0)
{
/*不一致須要所有返回整個文件, 時間比較時同樣*/
goto next_filter;
}
goto parse;
}
if (r->headers_out.last_modified_time == (time_t) -1) {
goto next_filter;
}
if_range_time = ngx_http_parse_time(if_range->data, if_range->len);
/*比較兩個時間是否一致*/
if (if_range_time != r->headers_out.last_modified_time) {
goto next_filter;
}
}
parse:
ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_range_filter_ctx_t));
if (ctx == NULL) {
return NGX_ERROR;
}
if (ngx_array_init(&ctx->ranges, r->pool, 1, sizeof(ngx_http_range_t))
!= NGX_OK)
{
return NGX_ERROR;
}
ranges = r->single_range ? 1 : clcf->max_ranges;
/*解析頭部送的Range字段 例如 Range: bytes=0-1024 */
switch (ngx_http_range_parse(r, ctx, ranges)) {
case NGX_OK:
ngx_http_set_ctx(r, ctx, ngx_http_range_body_filter_module);
r->headers_out.status = NGX_HTTP_PARTIAL_CONTENT;
r->headers_out.status_line.len = 0;
if (ctx->ranges.nelts == 1) {
/*只包含一個段時執行*/
return ngx_http_range_singlepart_header(r, ctx);
}
/*同時請求多個段時使用*/
return ngx_http_range_multipart_header(r, ctx);
/*客戶端請求的Range字段格式不正確, 直接返回給客戶端錯誤*/
case NGX_HTTP_RANGE_NOT_SATISFIABLE:
return ngx_http_range_not_satisfiable(r);
case NGX_ERROR:
return NGX_ERROR;
default: /* NGX_DECLINED */
break;
}
next_filter:
r->headers_out.accept_ranges = ngx_list_push(&r->headers_out.headers);
if (r->headers_out.accept_ranges == NULL) {
return NGX_ERROR;
}
r->headers_out.accept_ranges->hash = 1;
/*輸出 Accept-Ranges : bytes 字段告訴客戶端, 服務器支持分段下載*/
ngx_str_set(&r->headers_out.accept_ranges->key, "Accept-Ranges");
ngx_str_set(&r->headers_out.accept_ranges->value, "bytes");
return ngx_http_next_header_filter(r);
}
而後解析Range字段，若是字段中只有一個範圍字段，則經過ngx_http_range_singlepart_header函數進行解析過濾，函數比較簡單只是設置返回頭部Content-Range字段。若是請求的多個範圍經過函數ngx_http_range_multipart_header進行解析過濾，函數會生成boundary字段（一個全局變量上面每次加1生成），並設置ngx_http_range_filter_ctx_t和ngx_http_range_t中頭部信息。服務器
static ngx_int_t
ngx_http_range_multipart_header(ngx_http_request_t *r,
ngx_http_range_filter_ctx_t *ctx)
{
size_t len;
ngx_uint_t i;
ngx_http_range_t *range;
ngx_atomic_uint_t boundary;
len = sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN
+ sizeof(CRLF "Content-Type: ") - 1
+ r->headers_out.content_type.len
+ sizeof(CRLF "Content-Range: bytes ") - 1;
/*判斷是否須要添加charset字段, 若是添加charset字段, content_type.len 和 content_type_len值將不會相等.*/
if (r->headers_out.content_type_len == r->headers_out.content_type.len
&& r->headers_out.charset.len)
{
len += sizeof("; charset=") - 1 + r->headers_out.charset.len;
}
ctx->boundary_header.data = ngx_pnalloc(r->pool, len);
if (ctx->boundary_header.data == NULL) {
return NGX_ERROR;
}
/*全局變量上加1, 做爲分割符*/
boundary = ngx_next_temp_number(0);
/*
* The boundary header of the range:
* CRLF
* "--0123456789" CRLF
* "Content-Type: image/jpeg" CRLF
* "Content-Range: bytes "
*/
/*因爲存在多個段, 所以內容中須要有分割符區分, 下面設置分割符*/
if (r->headers_out.content_type_len == r->headers_out.content_type.len
&& r->headers_out.charset.len)
{
ctx->boundary_header.len = ngx_sprintf(ctx->boundary_header.data,
CRLF "--%0muA" CRLF
"Content-Type: %V; charset=%V" CRLF
"Content-Range: bytes ",
boundary,
&r->headers_out.content_type,
&r->headers_out.charset)
- ctx->boundary_header.data;
} else if (r->headers_out.content_type.len) {
ctx->boundary_header.len = ngx_sprintf(ctx->boundary_header.data,
CRLF "--%0muA" CRLF
"Content-Type: %V" CRLF
"Content-Range: bytes ",
boundary,
&r->headers_out.content_type)
- ctx->boundary_header.data;
} else {
ctx->boundary_header.len = ngx_sprintf(ctx->boundary_header.data,
CRLF "--%0muA" CRLF
"Content-Range: bytes ",
boundary)
- ctx->boundary_header.data;
}
r->headers_out.content_type.data =
ngx_pnalloc(r->pool,
sizeof("Content-Type: multipart/byteranges; boundary=") - 1
+ NGX_ATOMIC_T_LEN);
if (r->headers_out.content_type.data == NULL) {
return NGX_ERROR;
}
r->headers_out.content_type_lowcase = NULL;
/* "Content-Type: multipart/byteranges; boundary=0123456789" */
/* 設置頭部Content-Type類型,標識爲多段內容, 並指明分隔符boundary字段 */
r->headers_out.content_type.len =
ngx_sprintf(r->headers_out.content_type.data,
"multipart/byteranges; boundary=%0muA",
boundary)
- r->headers_out.content_type.data;
r->headers_out.content_type_len = r->headers_out.content_type.len;
r->headers_out.charset.len = 0;
/* the size of the last boundary CRLF "--0123456789--" CRLF */
len = sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN + sizeof("--" CRLF) - 1;
/* 循環設置每一個分段長度 */
range = ctx->ranges.elts;
for (i = 0; i < ctx->ranges.nelts; i++) {
/* the size of the range: "SSSS-EEEE/TTTT" CRLF CRLF */
range[i].content_range.data =
ngx_pnalloc(r->pool, 3 * NGX_OFF_T_LEN + 2 + 4);
if (range[i].content_range.data == NULL) {
return NGX_ERROR;
}
range[i].content_range.len = ngx_sprintf(range[i].content_range.data,
"%O-%O/%O" CRLF CRLF,
range[i].start, range[i].end - 1,
r->headers_out.content_length_n)
- range[i].content_range.data;
len += ctx->boundary_header.len + range[i].content_range.len
+ (size_t) (range[i].end - range[i].start);
}
r->headers_out.content_length_n = len;
if (r->headers_out.content_length) {
r->headers_out.content_length->hash = 0;
r->headers_out.content_length = NULL;
}
return ngx_http_next_header_filter(r);
}
內容過濾
入口函數ngx_http_range_body_filter，一樣分爲兩種狀況處理，一次請求一段的ngx_http_range_singlepart_body比較簡單，再也不說明。一次請求多個部分的ngx_http_range_multipart_body，首先判斷全部請求的範圍是否在同一個buffer上, nginx多段請求時,只處理文件內容或文件在同一個buffer上面的狀況。數據結構
static ngx_int_t
ngx_http_range_multipart_body(ngx_http_request_t *r,
ngx_http_range_filter_ctx_t *ctx, ngx_chain_t *in)
{
ngx_buf_t *b, *buf;
ngx_uint_t i;
ngx_chain_t *out, *hcl, *rcl, *dcl, **ll;
ngx_http_range_t *range;
ll = &out;
buf = in->buf;
range = ctx->ranges.elts;
/*
* 重組須要分段的buf, 首先是分段分隔符頭部, 分段長度, 分段內容, 重組成一個新的鏈表
*/
for (i = 0; i < ctx->ranges.nelts; i++) {
/*
* The boundary header of the range:
* CRLF
* "--0123456789" CRLF
* "Content-Type: image/jpeg" CRLF
* "Content-Range: bytes "
*/
b = ngx_calloc_buf(r->pool);
if (b == NULL) {
return NGX_ERROR;
}
b->memory = 1;
b->pos = ctx->boundary_header.data;
b->last = ctx->boundary_header.data + ctx->boundary_header.len;
hcl = ngx_alloc_chain_link(r->pool);
if (hcl == NULL) {
return NGX_ERROR;
}
hcl->buf = b;
/* "SSSS-EEEE/TTTT" CRLF CRLF */
b = ngx_calloc_buf(r->pool);
if (b == NULL) {
return NGX_ERROR;
}
b->temporary = 1;
b->pos = range[i].content_range.data;
b->last = range[i].content_range.data + range[i].content_range.len;
rcl = ngx_alloc_chain_link(r->pool);
if (rcl == NULL) {
return NGX_ERROR;
}
rcl->buf = b;
/* the range data */
b = ngx_calloc_buf(r->pool);
if (b == NULL) {
return NGX_ERROR;
}
b->in_file = buf->in_file;
b->temporary = buf->temporary;
b->memory = buf->memory;
b->mmap = buf->mmap;
b->file = buf->file;
if (buf->in_file) {
b->file_pos = buf->file_pos + range[i].start;
b->file_last = buf->file_pos + range[i].end;
}
if (ngx_buf_in_memory(buf)) {
b->pos = buf->pos + (size_t) range[i].start;
b->last = buf->pos + (size_t) range[i].end;
}
dcl = ngx_alloc_chain_link(r->pool);
if (dcl == NULL) {
return NGX_ERROR;
}
dcl->buf = b;
/*hcl(分隔符頭), rcl(分段長度), dcl(分段內容) 串成新的鏈表*/
*ll = hcl;
hcl->next = rcl;
rcl->next = dcl;
ll = &dcl->next;
}
/* the last boundary CRLF "--0123456789--" CRLF */
b = ngx_calloc_buf(r->pool);
if (b == NULL) {
return NGX_ERROR;
}
b->temporary = 1;
b->last_buf = 1;
b->pos = ngx_pnalloc(r->pool, sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN
+ sizeof("--" CRLF) - 1);
if (b->pos == NULL) {
return NGX_ERROR;
}
b->last = ngx_cpymem(b->pos, ctx->boundary_header.data,
sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN);
*b->last++ = '-'; *b->last++ = '-';
*b->last++ = CR; *b->last++ = LF;
hcl = ngx_alloc_chain_link(r->pool);
if (hcl == NULL) {
return NGX_ERROR;
}
hcl->buf = b;
hcl->next = NULL;
*ll = hcl;
return ngx_http_next_body_filter(r, out);
}
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