libcurl 考古

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晚上在浏览 curl github 上的 tag, 好奇心驱使。我翻到了 curl 的第一个 release tag: curl-6_5

tag 的创建日期是 2000年5月14日，至今已经20余年了，当时我才读小学，有种穿越时空的奇妙感觉。

一直想学习一些 curl 的源码，可惜最新版本的代码量太大了，数据结构和调用关系错综复杂无从入手。第一版本应该是只支持了最基础的功能，果断下载。

相比之下，代码量少了很多。结构也简单明了不少。

对照着官方的release note，以及commit id，学习大佬怎么一步一步把 curl 做成今天的样子，真有挖到宝藏的感觉。

这是官方 doc. 里最早的几个版本的 release note

附录

RESOURCES 文件记录了一些 RFC 文档

  • RFC 959 - Defines how FTP works
  • RFC 1738 - Uniform Resource Locators
  • RFC 1777 - defines the LDAP protocol
  • RFC 1808 - Relative Uniform Resource Locators

  • RFC 1867 - Form-based File Upload in HTML

  • RFC 1950 - ZLIB Compressed Data Format Specification

  • RFC 1951 - DEFLATE Compressed Data Format Specification

  • RFC 1952 - gzip compression format

  • RFC 1959 - LDAP URL syntax

  • RFC 2045-2049 - Everything you need to know about MIME! (needed for form based upload)
  • RFC 2068 - HTTP 1.1 (obsoleted by RFC 2616)
  • RFC 2109 - HTTP State Management Mechanism (cookie stuff)
  • Netscape’s specification at http://www.netscape.com/newsref/std/cookie_spec.html
  • RFC 2183 - “The Content-Disposition Header Field”
  • RFC 2229 - “A Dictionary Server Protocol”
  • RFC 2231 - “MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations”
  • RFC 2388 - “Returning Values from Forms: multipart/form-data” Use this as an addition to the 1867
  • RFC 2396 - “Uniform Resource Identifiers: Generic Syntax and Semantics”
  • RFC 2428 - “FTP Extensions for IPv6 and NATs”
  • RFC 2616 - HTTP 1.1
  • RFC 2617 - HTTP Authentication

FEATURES 文件记录了支持的 feature

  1. Misc

    • full URL syntax
    • custom maximum download time
    • custom least download speed acceptable
    • multiple URLs
    • guesses protocol from host name unless specified
    • uses .netrc
    • progress bar/time specs while downloading
    • PROXY environment variables support
    • config file support
    • compiles on win32

  2. HTTP

    • GET
    • PUT
    • HEAD
    • POST
    • multipart POST
    • authentication
    • resume
    • follow redirects
    • custom HTTP request
    • cookie get/send
    • custom headers (that can replace internally generated headers)
    • custom user-agent string
    • custom referer string
    • range
    • proxy authentication
    • time conditions
    • via http-proxy

  3. HTTPS (*1)

    • (all the HTTP features)
    • using certificates
    • via http-proxy

  4. FTP

    • download
    • authentication
    • PORT or PASV
    • single file size information (compare to HTTP HEAD)
    • ‘type=’ URL support
    • dir listing
    • dir listing names-only
    • upload
    • upload append
    • upload via http-proxy as HTTP PUT
    • download resume
    • upload resume
    • QUOT commands (before and/or after the transfer)
    • simple “range” support
    • via http-proxy

  5. TELNET

    • connection negotiation
    • stdin/stdout I/O

  6. LDAP (*2)

    • full LDAP URL support

  7. DICT

    • extended DICT URL support

  8. GOPHER

    • GET
    • via http-proxy

  9. FILE

    • URL support

      1 = requires OpenSSL 2 = requires OpenLDAP