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Niels Lohmann
6baf56a239
unflatten() split every key into a vector of reference tokens, stored the pointer prefixes in a tree to decide which values become arrays, and then looked up every token of every key from the root again. Keys are now checked by a scan that raises the same parse_error.107/108 as split(), skipping the part a key shares with the previous one, which was checked already. The prefixes that denote arrays are kept in a small hash set of key slices; the array/object decision is unchanged. The walk keeps the values along the previous key's path, so only the part of a key that differs from the previous one is looked up. Keys of a flattened object are usually sorted, so that part is short. unflatten() of canada.json, citm_catalog.json and twitter.json is 1.9x to 2.3x as fast; the output and the exceptions are unchanged. Signed-off-by: Niels Lohmann <mail@nlohmann.me>