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std/headers

std/headers

Section titled “std/headers”

std/headers — HTTP HeaderMap with case-insensitive lookup, multi-valued entries, and insertion-ordered iteration. Backs the headers: HeaderMap field that’s slated to land on HttpRequest and HttpResponse (docs/STDLIB-DESIGN-RESEARCH.md Rec §2). This PR lands the type + methods only; the HttpRequest / HttpResponse wiring + the wasi-http canonical-ABI fields- resource integration follow in their own reviewable units. Storage: two parallel arrays. names holds case-folded (lowercase) header names so lookup compares against the same form the caller passes through to_lower(); values holds the raw value at the matching index in insertion order. Linear- scan lookup is fine for the typical <20-header request, matches the spirit of hyper’s HeaderMap, and avoids the IndexMap indexing-table overhead until profiling says otherwise. Invariants: - len(h.names) == len(h.values). - h.names[i] is always lowercase ASCII. - Iteration / append order is insertion order; .set replaces in-place at the existing index and drops any additional duplicates further down.

header_map_new

Section titled “header_map_new”
pub function header_map_new(): HeaderMap

header_map_new() — empty HeaderMap. Use when constructing HttpRequest / HttpResponse from lang code (the wasi-http wrapper + http_parse_request will populate one for you on the inbound path once the integration PR lands).

get

Section titled “get”
pub function (h: HeaderMap) get(name: string): Option[string]

.get(name) — first value for name, case-insensitive. Returns None when no entry matches; use .get_all when duplicates matter (Set-Cookie, Accept, Via).

get_all

Section titled “get_all”
pub function (h: HeaderMap) get_all(name: string): string[]

.get_all(name) — every value for name in insertion order. Returns an empty array when no entry matches (callers shouldn’t need to special-case “missing” separately from “present but empty list”).

append

Section titled “append”
pub function (h: HeaderMap) append(name: string, value: string): HeaderMap

.append(name, value) — add an entry without replacing existing entries with the same name. The canonical “I want duplicate-safe insertion” call (headers.append("Set-Cookie", "...") keeps each cookie distinct).

set

Section titled “set”
pub function (h: HeaderMap) set(name: string, value: string): HeaderMap

.set(name, value) — replace any/all existing entries for name with a single new entry. Position-stable: if name already existed at index k, the new value lands at index k and further duplicates are dropped; if name was absent, the new entry appends.

len

Section titled “len”
pub function (h: HeaderMap) len(): i32

.len() — total entries (duplicates counted separately). h = h.set("Set-Cookie", "a"); h = h.append("Set-Cookie", "b"); h.len() is 2. (set/append are functional — rebind.)