From 5d7d5521e991ad1be99c9e7566e79486885abf34 Mon Sep 17 00:00:00 2001
From: Yarchik <spoko.dev@gmail.com>
Date: Tue, 23 Jun 2026 00:18:22 +0100
Subject: [PATCH 1/3] fix: clamp a suffix range whose length exceeds the
 representation
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`bytes=-N` where N is larger than the representation size was rejected as
unsatisfiable instead of using the whole representation:

    parse(100, 'bytes=-101') // -1   (expected [{ start: 0, end: 99 }])
    parse(100, 'bytes=-500') // -1

RFC 7233 §2.1: "If the selected representation is shorter than the
specified suffix-length, the entire representation is used." The parser
already clamps the analogous last-byte-pos overflow (`bytes=0-9999`); the
suffix form just missed it, letting `start = size - suffixLength` go
negative and get dropped. Clamp that start to 0. `bytes=-0` and an empty
representation stay unsatisfiable.
---
 index.js             | 5 +++++
 test/range-parser.js | 7 +++++++
 2 files changed, 12 insertions(+)

diff --git a/index.js b/index.js
index 41e1cd3..7bfdbf8 100644
--- a/index.js
+++ b/index.js
@@ -59,6 +59,11 @@ function rangeParser (size, str, options) {
     if (startStr.length === 0) {
       start = size - end
       end = size - 1
+
+      // a suffix-length larger than the representation uses the whole representation
+      if (start < 0) {
+        start = 0
+      }
     } else if (endStr.length === 0) {
       end = size - 1
     }
diff --git a/test/range-parser.js b/test/range-parser.js
index 9f2c483..5a23854 100644
--- a/test/range-parser.js
+++ b/test/range-parser.js
@@ -109,6 +109,13 @@ describe('parseRange(len, str)', function () {
     deepEqual(range[0], { start: 600, end: 999 })
   })
 
+  it('should use the whole representation when the suffix-length is larger', function () {
+    var range = parse(100, 'bytes=-101')
+    assert.strictEqual(range.type, 'bytes')
+    assert.strictEqual(range.length, 1)
+    deepEqual(range[0], { start: 0, end: 99 })
+  })
+
   it('should parse str with only start', function () {
     var range = parse(1000, 'bytes=400-')
     assert.strictEqual(range.type, 'bytes')

From 50a64681b3e897749090bab0aea28c76333d502f Mon Sep 17 00:00:00 2001
From: Blake Embrey <hello@blakeembrey.com>
Date: Thu, 25 Jun 2026 13:04:03 -0700
Subject: [PATCH 2/3] Use Math.max

---
 index.js | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/index.js b/index.js
index 7bfdbf8..ad2b6cc 100644
--- a/index.js
+++ b/index.js
@@ -57,13 +57,8 @@ function rangeParser (size, str, options) {
     var end = parsePos(endStr)
 
     if (startStr.length === 0) {
-      start = size - end
+      start = Math.max(size - end, 0)
       end = size - 1
-
-      // a suffix-length larger than the representation uses the whole representation
-      if (start < 0) {
-        start = 0
-      }
     } else if (endStr.length === 0) {
       end = size - 1
     }
@@ -79,7 +74,7 @@ function rangeParser (size, str, options) {
     }
 
     // skip unsatisfiable ranges
-    if (start > end || start < 0) {
+    if (start > end) {
       valid = true
       continue
     }

From da93ab26d640b2d50e8c1dbe1cf950437403211e Mon Sep 17 00:00:00 2001
From: Blake Embrey <hello@blakeembrey.com>
Date: Thu, 25 Jun 2026 13:46:05 -0700
Subject: [PATCH 3/3] Add -0 to test cases

---
 test/range-parser.js | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/test/range-parser.js b/test/range-parser.js
index 5a23854..5147754 100644
--- a/test/range-parser.js
+++ b/test/range-parser.js
@@ -109,6 +109,11 @@ describe('parseRange(len, str)', function () {
     deepEqual(range[0], { start: 600, end: 999 })
   })
 
+  it('should be unsatisfiable asking for -0', function () {
+    var range = parse(1000, 'bytes=-0')
+    assert.strictEqual(range, -1)
+  })
+
   it('should use the whole representation when the suffix-length is larger', function () {
     var range = parse(100, 'bytes=-101')
     assert.strictEqual(range.type, 'bytes')