Hex bytes slice

hex-bytes-slice · version 1.0.0 · Encoding & checksums · free, no key needed

Slice a lowercase hex byte string by explicit byte-index bounds, half-open like Array.slice.

Use when you need to: hex bytes slice · slice hex byte string · byte-range slice of hex.

Supported

hex bytes slice
slice hex byte string
byte-range slice of hex

Not supported

negative indexes
python wrap-around slicing
uppercase hex
0x prefix
code-point or character slicing
decode hex to text

Behavior

hex is a lowercase hex byte string: 0-9 and a-f only, two hex digits per byte, no 0x prefix, no separators, no whitespace, no uppercase.
hex is bounded to 128000 bytes (256000 hex characters).
start and end are JSON integers with Number.isInteger, each between 0 and the byte-count bound, counting whole bytes (not hex characters).
The slice is the half-open byte interval [start, end): the byte at index end is not included.
end must be greater than or equal to start; start and end must each be at most the byte length of hex. Negative indexes, wrap-around, and end < start are rejected rather than reinterpreted.
A slice where start equals end is allowed at any valid position and returns an empty result.

Input

hex (string, required): max length 256000
start (integer, required): min 0; max 128000
end (integer, required): min 0; max 128000

Output

hex (string, required)

Limits

max input bytes: 128000
max index: 128000

Example

Request input:

{
  "hex": "aabbccdd",
  "start": 1,
  "end": 3
}

Response:

{
  "result": {
    "hex": "bbcc"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "hex-bytes-slice",
  "version": "1.0.0",
  "input": {
    "hex": "aabbccdd",
    "start": 1,
    "end": 3
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/hex-bytes-slice/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"hex":"aabbccdd","start":1,"end":3}'

The machine-readable contract is at /v1/tools/hex-bytes-slice/versions/1.0.0.

CLI

node cli.mjs run hex-bytes-slice 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Hex bytes xor: Byte-wise XOR of two equal-length lowercase hex byte strings. Transformation only; no cryptographic security claim.
Hex bytes concat: Concatenate a bounded ordered list of lowercase hex byte strings into one hex string.
UTF-8 hex: Encode a Unicode string as lowercase hex of its UTF-8 bytes. Transformation only; no security claim.
Adler-32: Adler-32 of UTF-8 bytes (RFC 1950). Integrity check only; no security claim.
Base64 UTF-8: Decode standard Base64 to UTF-8 text. Transformation only; no security claim.
CRC-32: CRC-32 of UTF-8 bytes (ISO 3309 / ZIP / PNG polynomial). Integrity check only; no security claim.