Merge pull request #15 from SidOfc/patch/reduce-system-reads

patch/reduce system reads

src/extractors/avi.js

@@ -1,4 +1,4 @@
-import {lazystream, roundToPrecision} from '../util.js';
+import {lazystream} from '../util.js';
 
 export function attributes(input) {
     const stream = lazystream(input);

src/extractors/fit.js

@@ -9,29 +9,24 @@ export function attributes(input) {
         mime: 'image/fits',
     };
 
-    let offset = 0;
-
     while (stream.more()) {
-        const label = stream
-            .goto(offset * 80)
-            .takeUntil(0x20)
-            .toString();
-
-        if (label === 'NAXIS1' || label === 'NAXIS2') {
-            const property = label === 'NAXIS1' ? 'width' : 'height';
-            result[property] = parseInt(
-                stream
-                    .goto(offset * 80)
-                    .skip(24)
-                    .take(8)
-                    .toString()
-                    .trim()
-            );
-
-            if (result.width !== 0 && result.height !== 0) break;
+        const header = stream.take(30);
+        const label = header.subarray(0, 8);
+
+        if (label.includes('NAXIS1')) {
+            result.width = parseInt(header.subarray(22, 30));
+        } else if (label.includes('NAXIS2')) {
+            result.height = parseInt(header.subarray(22, 30));
+
+            break;
+        } else if (
+            label.includes('NAXIS') &&
+            parseInt(header.subarray(22, 30)) < 2
+        ) {
+            break;
         }
 
-        offset += 1;
+        stream.skip(50);
     }
 
     stream.close();

src/extractors/hdr.js

@@ -9,21 +9,19 @@ export function attributes(input) {
         mime: 'image/vnd.radiance',
     };
 
-    while (stream.more()) {
-        const line = stream.takeLine().toString();
+    for (const chunk of stream.overlappingChunks(64)) {
+        const content = chunk.buffer.toString();
+        const matches = content.match(/[-+][xy]\s+\d+\s/gi);
 
-        if (line.match(/[-+][xy]/i)) {
-            const parts = line
-                .split(' ')
-                .map((part) => part.replace(/[^a-z0-9]/gi, '').toUpperCase());
+        if (matches?.length === 2) {
+            for (const match of matches) {
+                const cleanMatch = match.toLowerCase().trim().slice(1);
+                const [axis, stringSize] = cleanMatch.split(/\s+/i);
 
-            if (parts[0] === 'Y') {
-                result.width = parseInt(parts[3], 10);
-                result.height = parseInt(parts[1], 10);
-            } else {
-                result.width = parseInt(parts[1], 10);
-                result.height = parseInt(parts[3], 10);
+                if (axis === 'x') result.width = parseInt(stringSize);
+                if (axis === 'y') result.height = parseInt(stringSize);
             }
+
             break;
         }
     }

src/extractors/j2c.js

@@ -2,8 +2,9 @@ import {lazystream} from '../util.js';
 
 export function attributes(input) {
     const stream = lazystream(input);
-    const height = stream.skip(48).takeUInt32BE();
-    const width = stream.takeUInt32BE();
+    const dimensions = stream.skip(48).take(8);
+    const height = dimensions.readUInt32BE();
+    const width = dimensions.readUInt32BE(4);
     const result = {width, height, size: stream.size(), mime: 'image/jp2'};
 
     stream.close();

src/extractors/jpg.js

@@ -12,14 +12,18 @@ export function attributes(input) {
     stream.skip(4);
 
     while (stream.more()) {
-        const size = stream.takeUInt16BE();
-        const mark = stream.skip(size - 2).takeUInt8();
-        const next = stream.takeUInt8();
+        stream.skip(stream.takeUInt16BE() - 2);
+
+        const header = stream.take(2);
+        const mark = header.readUInt8();
+        const next = header.readUInt8(1);
 
         if (mark !== 0xff) break;
         if (next === 0xc0 || next === 0xc1 || next === 0xc2) {
-            result.height = stream.skip(3).takeUInt16BE();
-            result.width = stream.takeUInt16BE();
+            const dimensions = stream.skip(3).take(4);
+
+            result.height = dimensions.readUInt16BE();
+            result.width = dimensions.readUInt16BE(2);
 
             break;
         }

src/extractors/mp4.js

@@ -22,19 +22,25 @@ export function attributes(input) {
 
 function parse(stream, lastTkhd) {
     while (stream.more()) {
-        const initialSize = stream.takeUInt32BE();
-        const header = stream.take(4).toString();
-        const size = initialSize === 1 ? stream.takeUInt64BE() : initialSize;
-
-        if (['moov', 'mdia', 'trak'].includes(header)) {
+        const header = stream.take(8);
+        const initialSize = header.readUInt32BE();
+        const type = header.subarray(4, 8).toString();
+        const size =
+            initialSize === 1
+                ? stream.takeUInt64BE()
+                : initialSize === 0
+                ? stream.size() - stream.position() + header.length
+                : initialSize;
+
+        if (['moov', 'mdia', 'trak'].includes(type)) {
             const result = parse(stream, lastTkhd);
 
             if (result) return result;
-        } else if (header === 'tkhd') {
-            lastTkhd = stream.take(size - 8);
+        } else if (type === 'tkhd') {
+            lastTkhd = stream.take(size - header.length);
 
-            stream.rewind(size - 8);
-        } else if (header === 'hdlr') {
+            stream.rewind(size - header.length);
+        } else if (type === 'hdlr') {
             if (stream.skip(8).take(4).includes('vide')) {
                 return {
                     width: lastTkhd.readUInt32BE(lastTkhd.length - 8) / 65536,
@@ -45,7 +51,7 @@ function parse(stream, lastTkhd) {
             stream.rewind(12);
         }
 
-        stream.skip(size - 8);
+        stream.skip(size - header.length);
     }
 
     return {width: 0, height: 0};

src/extractors/png.js

@@ -2,34 +2,21 @@ import {lazystream} from '../util.js';
 
 export function attributes(input) {
     const stream = lazystream(input);
-    const isMNG = stream.take(4).includes('MNG');
-    const isFried = stream.skip(8).take(4).includes('CgBI');
+    const header = stream.take(16);
 
-    if (isFried) stream.skip(16);
+    if (header.includes('CgBI')) stream.skip(16);
 
-    const result = {
-        width: stream.takeUInt32BE(),
-        height: stream.takeUInt32BE(),
-        size: stream.size(),
-        mime: isMNG
-            ? 'video/x-mng'
-            : isAPNG(stream)
-            ? 'image/apng'
-            : 'image/png',
-    };
+    const dimensions = stream.take(8);
+    const width = dimensions.readUInt32BE();
+    const height = dimensions.readUInt32BE(4);
+    const mime = header.includes('MNG')
+        ? 'video/x-mng'
+        : stream.take(128).includes('acTL')
+        ? 'image/apng'
+        : 'image/png';
+    const result = {width, height, size: stream.size(), mime};
 
     stream.close();
 
     return result;
 }
-
-function isAPNG(stream) {
-    const position = stream.position();
-    const result = [256, 512, 1024].some((size) =>
-        stream.take(size).includes('acTL')
-    );
-
-    stream.goto(position);
-
-    return result;
-}

src/extractors/pnm.js

@@ -1,6 +1,5 @@
 import {lazystream} from '../util.js';
 
-const WHITESPACE = [0x20, 0x09, 0x0d, 0x0a];
 const MIME_TYPES = {
     ['PF']: 'application/x-font-type1',
     ['P1']: 'image/x-portable-bitmap',
@@ -14,7 +13,7 @@ const MIME_TYPES = {
 
 export function attributes(input) {
     const stream = lazystream(input);
-    const type = stream.take(2).toString();
+    const type = stream.take(3).toString().trim();
     const attrs = type === 'P7' ? pam(stream) : pnm(stream);
     const result = {
         ...attrs,
@@ -29,43 +28,33 @@ export function attributes(input) {
 
 function pnm(stream) {
     while (stream.more()) {
-        const byte = stream.take()[0];
+        const line = stream.takeLine().toString();
 
-        if (WHITESPACE.includes(byte)) {
-            continue;
-        } else if (byte === 0x23) {
-            stream.skipLine();
-        } else {
-            stream.rewind(1);
+        if (line.match(/^\d+\s+\d+/)) {
+            const [widthString, heightString] = line.split(/\s+/);
 
-            break;
+            return {
+                width: parseInt(widthString),
+                height: parseInt(heightString),
+            };
         }
     }
-
-    return {
-        width: parseInt(stream.takeUntil(WHITESPACE).toString(), 10),
-        height: parseInt(
-            stream.skipWhile(WHITESPACE).takeUntil(WHITESPACE).toString(),
-            10
-        ),
-    };
 }
 
 function pam(stream) {
     const result = {width: 0, height: 0};
 
     while (stream.more()) {
-        const key = stream.takeUntil(WHITESPACE).toString();
+        const [key, stringSize] = stream
+            .takeLine()
+            .toString()
+            .toLowerCase()
+            .split(/\s+/i);
 
-        if (key === 'WIDTH' || key === 'HEIGHT') {
-            result[key.toLowerCase()] = parseInt(
-                stream.skipWhile(WHITESPACE).takeUntil(WHITESPACE).toString(),
-                10
-            );
+        if (key === 'width' || key === 'height') {
+            result[key] = parseInt(stringSize);
 
             if (result.width && result.height) break;
-        } else {
-            stream.skipLine();
         }
     }