HTTP包头中关于断点续传的字段定义

引用

The Content-Range entity-header is sent with a partial entity-body to specify where in the full entity-body the partial body should be applied.

HTTP 回应Content-Range用于指出在整个数据文件中发送部分的数据范围。

引用

A server sending a response with status code 416 (Requested range not satisfiable) SHOULD include a Content-Range field with a byte-range- resp-spec of "*". The instance-length specifies the current length of the selected resource. A response with status code 206 (Partial Content) MUST NOT include a Content-Range field with a byte-range- resp-spec of "*".

服务端回应状态代码416时Conten-Range字段的结束位置应该“*”星号。回应206不能使用"*"星号。

引用

Examples of byte-content-range-spec values, assuming that the entity contains a total of 1234 bytes:

      . The first 500 bytes:
       bytes 0-499/1234

      . The second 500 bytes:
       bytes 500-999/1234

      . All except for the first 500 bytes:
       bytes 500-1233/1234

      . The last 500 bytes:
       bytes 734-1233/1234

HTTP回应时指定Content-Length字段的值

引用

When an HTTP message includes the content of a single range (for example, a response to a request for a single range, or to a request for a set of ranges that overlap without any holes), this content is transmitted with a Content-Range header, and a Content-Length header showing the number of bytes actually transferred. For example,

       HTTP/1.1 206 Partial content
       Date: Wed, 15 Nov 1995 06:25:24 GMT
       Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
       Content-Range: bytes 21010-47021/47022
       Content-Length: 26012
       Content-Type: image/gif

引用

Byte range specifications in HTTP apply to the sequence of bytes in the entity-body
A byte range operation MAY specify a single range of bytes, or a set of ranges within a single entity.

       ranges-specifier = byte-ranges-specifier
       byte-ranges-specifier = bytes-unit "=" byte-range-set
       byte-range-set  = 1#( byte-range-spec | suffix-byte-range-spec )
       byte-range-spec = first-byte-pos "-" [last-byte-pos]
       first-byte-pos  = 1*DIGIT
       last-byte-pos   = 1*DIGIT

The first-byte-pos value in a byte-range-spec gives the byte-offset of the first byte in a range. The last-byte-pos value gives the byte-offset of the last byte in the range; that is, the byte positions specified are inclusive. Byte offsets start at zero.

用于HTTP请求时指出整个数据体中的起始和结束的字节串。偏移量从0开始。

参考：
http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html