@tldraw/state/dist-esm/lib/HistoryBuffer.mjs.map

tldraw infinite canvas SDK (state).

{
  "version": 3,
  "sources": ["../../src/lib/HistoryBuffer.ts"],
  "sourcesContent": ["import { RESET_VALUE } from './types'\n\ntype RangeTuple<Diff> = [fromEpoch: number, toEpoch: number, diff: Diff]\n\n/**\n * A structure that stores diffs between values of an atom.\n *\n * @internal\n */\nexport class HistoryBuffer<Diff> {\n\tprivate index = 0\n\n\t// use a wrap around buffer to store the last N values\n\tbuffer: Array<RangeTuple<Diff> | undefined>\n\n\tconstructor(private readonly capacity: number) {\n\t\tthis.buffer = new Array(capacity)\n\t}\n\n\t/**\n\t * Add a diff to the history buffer.\n\t *\n\t * @param lastComputedEpoch - The epoch when the diff was computed.\n\t * @param currentEpoch - The current epoch.\n\t * @param diff - The diff to add, or else a reset value.\n\t */\n\tpushEntry(lastComputedEpoch: number, currentEpoch: number, diff: Diff | RESET_VALUE) {\n\t\tif (diff === undefined) {\n\t\t\treturn\n\t\t}\n\n\t\tif (diff === RESET_VALUE) {\n\t\t\tthis.clear()\n\t\t\treturn\n\t\t}\n\n\t\t// Add the diff to the buffer as a range tuple.\n\t\tthis.buffer[this.index] = [lastComputedEpoch, currentEpoch, diff]\n\n\t\t// Bump the index, wrapping around if necessary.\n\t\tthis.index = (this.index + 1) % this.capacity\n\t}\n\n\t/**\n\t * Clear the history buffer.\n\t */\n\tclear() {\n\t\tthis.index = 0\n\t\tthis.buffer.fill(undefined)\n\t}\n\n\t/**\n\t * Get the diffs since the given epoch.\n\t *\n\t * @param sinceEpoch - The epoch to get diffs since.\n\t * @returns An array of diffs or a flag to reset the history buffer.\n\t */\n\tgetChangesSince(sinceEpoch: number): RESET_VALUE | Diff[] {\n\t\tconst { index, capacity, buffer } = this\n\n\t\t// For each item in the buffer...\n\t\tfor (let i = 0; i < capacity; i++) {\n\t\t\tconst offset = (index - 1 + capacity - i) % capacity\n\n\t\t\tconst elem = buffer[offset]\n\n\t\t\t// If there's no element in the offset position, return the reset value\n\t\t\tif (!elem) {\n\t\t\t\treturn RESET_VALUE\n\t\t\t}\n\n\t\t\tconst [fromEpoch, toEpoch] = elem\n\n\t\t\t// If the first element is already too early, bail\n\t\t\tif (i === 0 && sinceEpoch >= toEpoch) {\n\t\t\t\treturn []\n\t\t\t}\n\n\t\t\t// If the element is since the given epoch, return an array with all diffs from this element and all following elements\n\t\t\tif (fromEpoch <= sinceEpoch && sinceEpoch < toEpoch) {\n\t\t\t\tconst len = i + 1\n\t\t\t\tconst result = new Array(len)\n\n\t\t\t\tfor (let j = 0; j < len; j++) {\n\t\t\t\t\tresult[j] = buffer[(offset + j) % capacity]![2]\n\t\t\t\t}\n\n\t\t\t\treturn result\n\t\t\t}\n\t\t}\n\n\t\t// If we haven't returned yet, return the reset value\n\t\treturn RESET_VALUE\n\t}\n}\n"],
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