[Cyan]<Imaging>ISScanner>ISScan.mesa!3

ISScan.mesa

edit by Ayers 23-May-85 18:44:11

Rick Beach, August 1, 1985 3:08:52 pm PDT

MKaplan, September 13, 1985 2:33:29 pm PDT

DIRECTORY

Basics,

ISBinding,

ISToken,

ISNode,

IO USING [STREAM],

Rope;

ISScan: CEDAR DEFINITIONS

= BEGIN

ParseFailureReason: TYPE = {

unsupportedConstruct, unexpectedDelimiter,

hitEndOfScript, outOfPlaceConstruct, bindingAbsent, bindingWrongType, spare };

ParseFailure: SIGNAL [s: ScanHandle, r: ParseFailureReason];

ScanState: TYPE = {null, inProgress, complete, failed};

ScanStreamFlavor: TYPE = {characters, tokens};

bufferBytes: CARDINAL = 4;

Buffer: TYPE = PACKED ARRAY [0..bufferBytes) OF Basics.Byte;

The input stream. Can be a character stream, in which case chars are collected into tokens by ISScanImpl.TokenFromCharactersStream[], or a stream of tokens that are picked off, one by one, by ISScanImpl.TokenFromTokensStream[]. When a stream runs out, the current stream becomes the one in the pushed field, from which further tokens come. This gives an "include" facility: when you want to splice in a stream, set the input stream to a new one with the splice, its pushed field being the unspliced input stream.

ScanStream: TYPE = RECORD [

name: ATOM ← NIL,

pushed: REF ScanStream ← NIL,

token: ISToken.TVHandle ← NIL,

body: SELECT type: ScanStreamFlavor FROM

characters => [

cstream: IO.STREAM ← NIL,

inString: BOOLEAN ← FALSE],

tokens => [

tokenList: ISToken.TVHandle ← NIL],

ENDCASE ← NULL];

CharactersScanner: TYPE = REF characters ScanStream;

TokensScanner: TYPE = REF tokens ScanStream;

ScanObject: TYPE = RECORD [

scanState: ScanState ← null,

allocateWith: ISToken.ISNodeDotHandle,

bindingStack: ISBinding.StackHandle,

zoneIsScans, stackIsScans: BOOLEAN ← FALSE,

family: ATOM ← NIL,

stream: REF ScanStream

];

<<addedNode: CONDITION -- for syncing with scanning -->>

ScanHandle: TYPE = REF ScanObject;

CreateScan: PROCEDURE [

base: Rope.ROPE,

index: INT,

allocateWith: ISNode.Handle,

bindingStack: ISBinding.StackHandle ← NIL,

family: ATOM ← NIL ]

RETURNS [ScanHandle];

PushScan: PROCEDURE [ScanHandle, Rope.ROPE, ATOM];

PopScan: PROCEDURE [ScanHandle];

InitializeScan: PROCEDURE [ScanHandle];

InitializeScanThroughCurly: PROCEDURE [ScanHandle];

Advance scan gets a new token into scanHandle.token. It should be called whenever a token is used up by the parser.

AdvanceScan: PROCEDURE [ScanHandle];

Collect node returns a node parsed from scan. It assumes that scan has been positioned past the initial leftCurly token. It does much of the real work of the parser.

CollectNode: PROCEDURE [scan: ScanHandle, parent: ISNode.Handle ← NIL, bound: BOOL ← FALSE]

RETURNS [ISToken.NodeTVHandle];

END.