Separate ZIO and MBuffer data structures

  - lua_load no longer takes a null reader function

1 files changed, 81 insertions, 0 deletions

diff --git a/src/lzio.js b/src/lzio.js
new file mode 100644
index 0000000..919ed44
--- /dev/null
+++ b/src/lzio.js
@@ -0,0 +1,81 @@
+"use strict";
+
+const assert = require('assert');
+
+
+class MBuffer {
+    constructor() {
+        this.buffer = null;
+        this.n = 0;
+    }
+}
+
+class ZIO {
+    constructor(L, reader, data) {
+        this.L = L;           /* Lua state (for reader) */
+        assert(typeof reader == "function", "ZIO requires a reader");
+        this.reader = reader; /* reader function */
+        this.data = data;     /* additional data */
+        this.n = 0;           /* bytes still unread */
+        this.buffer = null;
+        this.off = 0;         /* current position in buffer */
+    }
+
+    zgetc () {
+        return ((this.n--) > 0) ? this.buffer[this.off++] : luaZ_fill(this);
+    }
+}
+
+const EOZ = -1;
+
+const luaZ_fill = function(z) {
+    let size;
+    let buff = z.reader(z.L, z.data);
+    if (buff === null)
+        return EOZ;
+    if (buff instanceof DataView) {
+        z.buffer = new Uint8Array(buff.buffer, buff.byteOffset, buff.byteLength);
+        z.off = 0;
+        size = buff.byteLength - buff.byteOffset;
+    } else {
+        assert(typeof buff !== "string", "Should only load binary of array of bytes");
+        z.buffer = buff;
+        z.off = 0;
+        size = buff.length;
+    }
+    if (size === 0)
+        return EOZ;
+    z.n = size - 1;
+    return z.buffer[z.off++];
+};
+
+/* b should be an array-like that will be set to bytes
+ * b_offset is the offset at which to start filling */
+const luaZ_read = function(z, b, b_offset, n) {
+    while (n) {
+        if (z.n === 0) { /* no bytes in buffer? */
+            if (luaZ_fill(z) === EOZ)
+                return n; /* no more input; return number of missing bytes */
+            else {
+                z.n++;  /* luaZ_fill consumed first byte; put it back */
+                z.off--;
+            }
+        }
+        let m = (n <= z.n) ? n : z.n; /* min. between n and z->n */
+        for (let i=0; i<m; i++) {
+            b[b_offset++] = z.buffer[z.off++];
+        }
+        z.n -= m;
+        if (z.n === 0) // remove reference to input so it can get freed
+            z.buffer = null;
+        n -= m;
+    }
+
+    return 0;
+};
+
+module.exports.EOZ       = EOZ;
+module.exports.luaZ_fill = luaZ_fill;
+module.exports.luaZ_read = luaZ_read;
+module.exports.MBuffer   = MBuffer;
+module.exports.ZIO       = ZIO;