.Dd $Mdocdate: March 12 2023 $
.Dt HTTP 3
.Os Telodendria Project
.Sh NAME
.Nm Http
.Nd Encode and decode various parts of the HTTP protocol.
.Sh SYNOPSIS
.In Http.h
.Ft const char *
.Fn HttpStatusToString "const HttpStatus"
.Ft HttpRequestMethod
.Fn HttpRequestMethodFromString "const char *"
.Ft const char *
.Fn HttpRequestMethodToString "const HttpRequestMethod"
.Ft char *
.Fn HttpUrlEncode "char *"
.Ft char *
.Fn HttpUrlDecode "char *"
.Ft HashMap *
.Fn HttpParamDecode "char *"
.Ft char *
.Fn HttpParamEncode "HashMap *"
.Ft HashMap *
.Fn HttpParseHeaders "FILE *"
.Sh DESCRIPTION
.Pp
.Nm
is a collection of utility functions that are useful for dealing with
HTTP. HTTP is not a complex protocol, but this API makes it a lot easier
to work with.
.Pp
.Fn HttpStatusToString
takes an HttpStatus and converts it into a string description of the
status, which is to be used in an HTTP response. For example, calling
.Fn HttpStatusToString "HTTP_GATEWAY_TIMEOUT"
produces the string "Gateway Timeout".
.Pp
HttpStatus is an enumeration that corresponds to the actual integer
values of the valid HTTP response codes. For example, calling
.Fn HttpStatusToString "504"
produces the same output. HttpStatus is defined as follows:
.Bd -literal -offset indent
typedef enum HttpStatus
{
    /* Informational responses */
    HTTP_CONTINUE = 100,
    HTTP_SWITCHING_PROTOCOLS = 101,
    HTTP_EARLY_HINTS = 103,

    /* Successful responses */
    HTTP_OK = 200,
    HTTP_CREATED = 201,
    HTTP_ACCEPTED = 202,
    HTTP_NON_AUTHORITATIVE_INFORMATION = 203,
    HTTP_NO_CONTENT = 204,
    HTTP_RESET_CONTENT = 205,
    HTTP_PARTIAL_CONTENT = 206,

    /* Redirection messages */
    HTTP_MULTIPLE_CHOICES = 300,
    HTTP_MOVED_PERMANENTLY = 301,
    HTTP_FOUND = 302,
    HTTP_SEE_OTHER = 303,
    HTTP_NOT_MODIFIED = 304,
    HTTP_TEMPORARY_REDIRECT = 307,
    HTTP_PERMANENT_REDIRECT = 308,

    /* Client error messages */
    HTTP_BAD_REQUEST = 400,
    HTTP_UNAUTHORIZED = 401,
    HTTP_FORBIDDEN = 403,
    HTTP_NOT_FOUND = 404,
    HTTP_METHOD_NOT_ALLOWED = 405,
    HTTP_NOT_ACCEPTABLE = 406,
    HTTP_PROXY_AUTH_REQUIRED = 407,
    HTTP_REQUEST_TIMEOUT = 408,
    HTTP_CONFLICT = 409,
    HTTP_GONE = 410,
    HTTP_LENGTH_REQUIRED = 411,
    HTTP_PRECONDITION_FAILED = 412,
    HTTP_PAYLOAD_TOO_LARGE = 413,
    HTTP_URI_TOO_LONG = 414,
    HTTP_UNSUPPORTED_MEDIA_TYPE = 415,
    HTTP_RANGE_NOT_SATISFIABLE = 416,
    HTTP_EXPECTATION_FAILED = 417,
    HTTP_TEAPOT = 418,
    HTTP_UPGRADE_REQUIRED = 426,
    HTTP_PRECONDITION_REQUIRED = 428,
    HTTP_TOO_MANY_REQUESTS = 429,
    HTTP_REQUEST_HEADER_FIELDS_TOO_LARGE = 431,
    HTTP_UNAVAILABLE_FOR_LEGAL_REASONS = 451,

    /* Server error responses */
    HTTP_INTERNAL_SERVER_ERROR = 500,
    HTTP_NOT_IMPLEMENTED = 501,
    HTTP_BAD_GATEWAY = 502,
    HTTP_SERVICE_UNAVAILABLE = 503,
    HTTP_GATEWAY_TIMEOUT = 504,
    HTTP_VERSION_NOT_SUPPORTED = 505,
    HTTP_VARIANT_ALSO_NEGOTIATES = 506,
    HTTP_NOT_EXTENDED = 510,
    HTTP_NETWORK_AUTH_REQUIRED = 511
} HttpStatus;
.Ed
.Pp
.Fn HttpRequestMethodFromString
and
.Fn HttpRequestMethodToString
convert an HttpRequestMethod enumeration value from and to a
string, respectively. The HttpRequestMethod enumeration is
defined as follows:
.Bd -literal -offset indent
typedef enum HttpRequestMethod
{
	HTTP_METHOD_UNKNOWN,
	HTTP_GET,
	HTTP_HEAD,
	HTTP_POST,
	HTTP_PUT,
	HTTP_DELETE,
	HTTP_CONNECT,
	HTTP_OPTIONS,
	HTTP_TRACE,
	HTTP_PATCH
} HttpRequestMethod;
.Ed
.Pp
These can be used for parsing a request method and then storing
it efficiently; it doesn't have be stored as a string, and it's
much nicer to work with enumeration values than it is with
strings in C. The very first enumeration value is not to be
passed to
.Fn HttpRequestMethodToString ,
rather it may be returned by
.Fn HttpRequestMethodFromString
if it cannot identify the request method string passed to it.
.Pp
.Fn HttpUrlEncode
and
.Fn HttpUrlDecode
deal with URL-safe strings.
.Fn HttpUrlEncode
encodes a C string such that it can appear in a URL, and
.Fn HttpUrlDecode
does the opposite; it decodes a URL string into the actual
bytes it is supposed to represent.
.Pp
.Fn HttpParamDecode
and
.Fn HttpParamEncode
convert HTTP parameters in the form of "param=value&param2=val2"
to and from a hash map for easy parsing, manipulation, and encoding.
.Pp
.Fn HttpParseHeaders
reads HTTP headers from a stream and returns a hash map
of keys and values. All keys are lowercased to make
querying them consistent and not dependent on the casing
that was read from the stream. This is useful for both
client and server code, since the headers are of the same
format. This function should be used after parsing the
HTTP status line, because it does not parse that line.
It will stop when it encounters the first blank line,
which indicates that the body is beginning. After this
function completes, the body may be immediately be read
from the stream without any additional processing.
.Sh RETURN VALUES
.Pp
.Fn HttpStatusToString
and
.Fn HttpRequestMethodToString
both return constant strings; they are not to be manipulated because
doing so would result in a segmentation fault, as these strings
are stored in the data segment of the program.
.Pp
.Fn HttpUrlEncode ,
.Fn HttpUrlDecode ,
.Fn HttpParamDecode ,
and
.Fn HttpParamEncode
all return strings that were allocated on the heap using the
Memory API, or NULL if there was an error allocating memory.
Thee strings returned can be manipulated at will, and must be
freed using the Memory API when they're no longer needed.
.Sh SEE ALSO
.Xr HashMap 3 ,
.Xr Memory 3