47 lines
1.6 KiB
Plaintext
47 lines
1.6 KiB
Plaintext
module wormhole::cursor {
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use std::vector::{Self};
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/// A cursor allows consuming a vector incrementally for parsing operations.
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/// It has no drop ability, and the only way to deallocate it is by calling the
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/// `destroy_empty` method, which will fail if the whole input hasn't been consumed.
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///
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/// This setup statically guarantees that the parsing methods consume the
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/// full input.
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struct Cursor<T> {
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data: vector<T>,
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}
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/// Initialises a cursor from a vector.
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public fun cursor_init<T>(data: vector<T>): Cursor<T> {
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// reverse the array so we have access to the first element easily
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vector::reverse(&mut data);
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Cursor<T> {
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data,
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}
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}
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/// Destroys an empty cursor.
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/// Aborts if the cursor is not empty.
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public fun destroy_empty<T>(cur: Cursor<T>) {
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let Cursor { data } = cur;
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vector::destroy_empty(data);
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}
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/// Consumes the rest of the cursor (thus destroying it) and returns the
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/// remaining bytes.
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/// NOTE: Only use this function if you intend to consume the rest of the
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/// bytes. Since the result is a vector, which can be dropped, it is not
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/// possible to statically guarantee that the rest will be used.
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public fun rest<T>(cur: Cursor<T>): vector<T> {
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let Cursor { data } = cur;
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// re-reverse the data so it is in the same order as the original input
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vector::reverse(&mut data);
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data
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}
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/// Returns the first element of the cursor and advances it.
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public fun poke<T>(cur: &mut Cursor<T>): T {
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vector::pop_back(&mut cur.data)
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}
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} |