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diff --git a/notes.md b/notes.md new file mode 100644 index 0000000..c3ccf30 --- /dev/null +++ b/notes.md @@ -0,0 +1,111 @@ +# URI + +[RFC 3986](https://tools.ietf.org/html/rfc3986) -- Uniform Resource Identifier (URI) + +## Example + + foo://example.com:8042/over/there?name=ferret#nose + \_/ \______________/\_________/ \_________/ \__/ + | | | | | + scheme authority path query fragment + | _____________________|__ + / \ / \ + urn:example:animal:ferret:nose + +## Elements + +* `IsRelative` -- flag indicating whether or not the reference is `relative reference` (as opposed to a `URI`) +* `Scheme` -- scheme name, if reference isn't relative +* `UserInfo` -- user information (user name, potentially with authorization information), if any is included +* `Host` -- host name or IP address, if included +* `Port` -- port number, if included +* `HasPort` -- flag indicating whether or not to include port number +* `Path` -- sequence of strings + * Include absolute path by making first element empty +* `Query` -- query string, if included +* `Fragment` -- fragment string, if included + +### Special disambiguation rules + +* `path-abempty`: For a `URI` with an `authority` component, the path must be either empty or absolute (first element empty); otherwise, it wouldn't possible to distinguish which characters belong to `host` and which belong to the path's first segment. +* `path-noscheme`: A `relative reference` cannot have a path whose first segment contains a colon (`:`) character; otherwise, its string representation would be ambiguous: it would also match a `URI` whose `scheme` is the part of the first segment of the path before the colon). + +### Notes + +* An empty string property indicates that it isn't included in the reference. +* A zero port number is still valid syntactically, so we need the separate `HasPort` property to indicate whether or not to include `Port`. +* The `authority` component is only included if `Host` is not empty, regardless of whether or not `UserInfo` is empty, and regardless of `HasPort`. +* If the first element of `Path` is an empty string, it indicates that the path is absolute. + +## Syntax + + URI-reference = URI / relative-ref + + URI = scheme ":" hier-part [ "?" query ] [ "#" fragment ] + absolute-URI = scheme ":" hier-part [ "?" query ] + relative-ref = relative-part [ "?" query ] [ "#" fragment ] + + relative-part = "//" authority path-abempty + / path-absolute + / path-noscheme + / path-empty + scheme = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." ) + hier-part = "//" authority path-abempty + / path-absolute + / path-rootless + / path-empty + query = *( pchar / "/" / "?" ) + fragment = *( pchar / "/" / "?" ) + + authority = [ userinfo "@" ] host [ ":" port ] + path = path-abempty ; begins with "/" or is empty + / path-absolute ; begins with "/" but not "//" + / path-noscheme ; begins with a non-colon segment + / path-rootless ; begins with a segment + / path-empty ; zero characters + path-abempty = *( "/" segment ) + path-absolute = "/" [ segment-nz *( "/" segment ) ] + path-noscheme = segment-nz-nc *( "/" segment ) + path-rootless = segment-nz *( "/" segment ) + path-empty = 0<pchar> + pchar = unreserved / pct-encoded / sub-delims / ":" / "@" + + userinfo = *( unreserved / pct-encoded / sub-delims / ":" ) + host = IP-literal / IPv4address / reg-name + port = *DIGIT + segment = *pchar + segment-nz = 1*pchar + segment-nz-nc = 1*( unreserved / pct-encoded / sub-delims / "@" ) + ; non-zero-length segment without any colon ":" + + IP-literal = "[" ( IPv6address / IPvFuture ) "]" + IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet + reg-name = *( unreserved / pct-encoded / sub-delims ) + + IPv6address = 6( h16 ":" ) ls32 + / "::" 5( h16 ":" ) ls32 + / [ h16 ] "::" 4( h16 ":" ) ls32 + / [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32 + / [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32 + / [ *3( h16 ":" ) h16 ] "::" h16 ":" ls32 + / [ *4( h16 ":" ) h16 ] "::" ls32 + / [ *5( h16 ":" ) h16 ] "::" h16 + / [ *6( h16 ":" ) h16 ] "::" + IPvFuture = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" ) + dec-octet = DIGIT ; 0-9 + / %x31-39 DIGIT ; 10-99 + / "1" 2DIGIT ; 100-199 + / "2" %x30-34 DIGIT ; 200-249 + / "25" %x30-35 ; 250-255 + + ls32 = ( h16 ":" h16 ) / IPv4address + ; least-significant 32 bits of address + h16 = 1*4HEXDIG + ; 16 bits of address represented in hexadecimal + + pct-encoded = "%" HEXDIG HEXDIG + unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~" + reserved = gen-delims / sub-delims + gen-delims = ":" / "/" / "?" / "#" / "[" / "]" / "@" + sub-delims = "!" / "$" / "&" / "'" / "(" / ")" + / "*" / "+" / "," / ";" / "=" |