Cursor-based character input layer for parsers, offering lookahead, mark/reset, source positions, span capture, in-memory and streaming inputs, plus small default token parsers (identifiers, quoted strings, whitespace, decimals).
kotlin-parsing-charinput is a Kotlin Multiplatform library for cursor-based character input in
parsers.
It provides lookahead, mark/reset, source positions, span capture, in-memory inputs, JVM/Android reader and file inputs, and small default parsers for common token shapes such as identifiers, quoted strings, whitespace, and decimal numbers.
Parser code often needs the same low-level operations:
kotlin-parsing-charinput keeps those concerns in one small API so higher-level parsers can focus
on grammar rules instead of cursor bookkeeping.
repositories {
mavenCentral()
}
dependencies {
implementation("one.wabbit:kotlin-parsing-charinput:1.2.0")
}
import one.wabbit.parsing.CharInput
import one.wabbit.parsing.DefaultParsers
import one.wabbit.parsing.StringStyle
val input = CharInput.withTextAndPosSpans("name = \"wabbit\"\n")
val key = DefaultParsers.readIdentifier(input)
DefaultParsers.skipHorizontalSpace(input)
check(input.takeExact("="))
DefaultParsers.skipHorizontalSpace(input)
val value = DefaultParsers.readString(input, StringStyle.Json)
check(key.value == "name")
check(value.value == "wabbit")
check(key.span.raw == "name")
check(key.span.start.line == 1L)
The parser functions advance the input as they succeed. The TextAndPosSpan factory captures both
the raw source text and the absolute start/end positions for every parsed token.
The companion factories choose how much capture data each span carries:
CharInput.withEmptySpans(input) captures no text or position data.CharInput.withPosOnlySpans(input) captures start and end positions.CharInput.withTextOnlySpans(input) captures raw source text.CharInput.withTextAndPosSpans(input) captures raw source text plus start and end positions.For custom span types, implement SpanFactory or SpanLike.
In-memory input is available on every supported target:
val input = CharInput.withTextOnlySpans("alpha beta")
JVM and Android also provide reader/file-backed inputs:
import java.io.StringReader
import one.wabbit.parsing.CharInput
import one.wabbit.parsing.TextOnlySpan
val input = CharInput.streaming(StringReader("alpha beta"), TextOnlySpan.spanLike)
The ring, streaming, and seekable factories are JVM/Android APIs. On native targets they throw
UnsupportedOperationException.
CharInput.current and CharInput.peek return CharInput.EOB at end of input. This is a sentinel,
not source text. Parser loops should check it before treating the current value as a real character.
This library is intended as a reusable low-level parser input layer. The core CharInput API and
the built-in span shapes are stable. The default token parsers are small convenience helpers rather
than a full parser-combinator framework.
Generated API docs can be built locally with Dokka. See API reference notes for the command.
This project is licensed under the GNU Affero General Public License v3.0 (AGPL-3.0) for open source use.
For commercial use, contact Wabbit Consulting Corporation at wabbit@wabbit.one.
Before contributions can be merged, contributors need to agree to the repository CLA.
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