1 files changed, 48 insertions, 0 deletions
diff --git a/llparse/src/implementation/c/node/consume.ts b/llparse/src/implementation/c/node/consume.ts
new file mode 100644
index 0000000..658a00e
--- /dev/null
+++ b/llparse/src/implementation/c/node/consume.ts
@@ -0,0 +1,48 @@
+import * as frontend from 'llparse-frontend';
+
+import { Compilation } from '../compilation';
+import { Node } from './base';
+
+export class Consume extends Node<frontend.node.Consume> {
+  public doBuild(out: string[]): void {
+    const ctx = this.compilation;
+
+    const index = ctx.stateField(this.ref.field);
+    const ty = ctx.getFieldType(this.ref.field);
+
+    let fieldTy: string;
+    if (ty === 'i64') {
+      fieldTy = 'uint64_t';
+    } else if (ty === 'i32') {
+      fieldTy = 'uint32_t';
+    } else if (ty === 'i16') {
+      fieldTy = 'uint16_t';
+    } else if (ty === 'i8') {
+      fieldTy = 'uint8_t';
+    } else {
+      throw new Error(
+        `Unsupported type ${ty} of field ${this.ref.field} for consume node`);
+    }
+
+    out.push('size_t avail;');
+    out.push(`${fieldTy} need;`);
+
+    out.push('');
+    out.push(`avail = ${ctx.endPosArg()} - ${ctx.posArg()};`);
+    out.push(`need = ${index};`);
+
+    // Note: `avail` or `need` are going to coerced to the largest
+    // datatype needed to hold either of the values.
+    out.push('if (avail >= need) {');
+    out.push(`  p += need;`);
+    out.push(`  ${index} = 0;`);
+    const tmp: string[] = [];
+    this.tailTo(tmp, this.ref.otherwise!);
+    ctx.indent(out, tmp, '  ');
+    out.push('}');
+    out.push('');
+
+    out.push(`${index} -= avail;`);
+    this.pause(out);
+  }
+}