Run Length Record Value First Offset

Description

Find the first logical offset of a literal value, retaining null when absent rather than using a sentinel position.

Run-length records represent repeated observations without expanding them. Each record pairs a literal string value with a positive exact integer length; neighboring equal values can be valid but noncompact. Expanded offsets count observations rather than run records, and half-open ranges include their start while excluding their end.

Find the first logical offset of a literal value, retaining null when absent rather than using a sentinel position.

When to use this tool

Use this tool to find the first logical offset of a literal value, retaining null when absent rather than using a sentinel position.

How to use the tool and how it works

Enter runsJson, value using the definitions below. Serialize JSON text fields in the decoded shape shown below.
Run the operation. Resolve input-format errors before interpreting an output.
Read result.offset, result.runIndex, using the stated boundary, ordering, sign and absence conventions.

Find the first original run with the exact value and sum preceding run lengths for its expanded offset. Return offset as decimal text and source runIndex, or null for both when absent.^[1]

Input field	Meaning and units	Accepted input
runsJson	JSON array of {value,length} records: literal string value and positive exact decimal-string length.	Text, at most 8,192 UTF-16 code units; narrower grammar/range rules also apply.
value	Exact literal string value to select, count or find.	Text, at most 8,192 UTF-16 code units; narrower grammar/range rules also apply.

These decoded structures show the examples inside JSON text fields. Supply their serialized JSON strings as input.

json

{
  "runsJson": [
    {
      "value": "a",
      "length": "3"
    },
    {
      "value": "a",
      "length": "2"
    },
    {
      "value": "b",
      "length": "4"
    }
  ]
}

Output field	Interpretation
result	Object containing the fields below.
result.offset	Exact expanded or within-run offset as decimal text, or null when a requested value is absent.
result.runIndex	Original zero-based containing/first-matching run index, or null when absent.

json

{
  "input": {
    "runsJson": "[{\"value\": \"a\", \"length\": \"3\"}, {\"value\": \"a\", \"length\": \"2\"}, {\"value\": \"b\", \"length\": \"4\"}]",
    "value": "b"
  },
  "output": {
    "result": {
      "offset": "5",
      "runIndex": 2
    }
  }
}

Limitations and assumptions

The source run layout is retained for provenance even when adjacent values are equal.
Run records contain string value and positive length as exact decimal integer text. Lengths and offset inputs support up to 256 decimal digits before operation-specific checks; results use decimal text and do not expand the repeated observations.
Every declared outer field is required and unknown outer fields are rejected. Strings and JSON text have size limits, lists are bounded to 128 entries, and JSON nesting/node counts are bounded. Tighter operation-specific bounds stated above take precedence.
Ordinary numeric outputs must be finite and within safe-integer magnitude. Exact large lengths/counts use decimal strings. Original record indexes and code-unit positions are zero-based; span ends are exclusive unless stated otherwise.

Alternative or Complementary methods

Use compaction for a canonical adjacent-run layout and boundary-aware operations when provenance matters. Retain exact decimal lengths rather than converting long totals to floating-point numbers.

References

Tool behavior and example: Run Length Record Value First Offset — tool.io

Similar or alternative tools

Run Length Record Value Map
Run lengths are positive exact integer decimal strings with literal string values, never expanded; map explicit literal values by a unique-key caller map and compact newly adjacent equal runs; mapping may deliberately merge values.
Run Length Record Value Selector
Run lengths are positive exact integer decimal strings with literal string values, never expanded; select complete runs by an explicit allowed-value bank, then compact adjacent remaining equal runs; logical positions close after removal.