Run Length Record Value Map

Description

Map explicit literal values by a unique-key caller map and compact newly adjacent equal runs; mapping may deliberately merge values.

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.

Map explicit literal values by a unique-key caller map and compact newly adjacent equal runs; mapping may deliberately merge values.

When to use this tool

Use this tool to map explicit literal values by a unique-key caller map and compact newly adjacent equal runs; mapping may deliberately merge values.

How to use the tool and how it works

Enter runsJson, names, replacements 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.runs, using the stated boundary, ordering, sign and absence conventions.

Require distinct mapping names aligned with replacements. Replace each exact matching run value once, leave unmatched values unchanged and compact adjacent equal results.^[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.
names	Distinct literal mapping keys aligned with replacements.	Dense list of at most 128 literal strings, each at most 8,192 UTF-16 units.
replacements	Literal replacement strings aligned with names; unmatched values remain unchanged.	Dense list of at most 128 literal strings, each at most 8,192 UTF-16 units.

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.runs	Resulting {value,length} records, with exact positive decimal lengths and the stated compaction policy.

json

{
  "input": {
    "runsJson": "[{\"value\": \"a\", \"length\": \"3\"}, {\"value\": \"a\", \"length\": \"2\"}, {\"value\": \"b\", \"length\": \"4\"}]",
    "names": [
      "b"
    ],
    "replacements": [
      "a"
    ]
  },
  "output": {
    "result": {
      "runs": [
        {
          "value": "a",
          "length": "9"
        }
      ]
    }
  }
}

Limitations and assumptions

Many original values may map to one replacement; no recursive substitution is performed.
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 Map — tool.io

Similar or alternative tools

Run Length Record Value First Offset
Run lengths are positive exact integer decimal strings with literal string values, never expanded; find the first logical offset of a literal value, retaining null when absent rather than using a sentinel position.
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.