Strings are length-and-hash-prefixed arrays of characters. If the string is ascii compatible, each character is a Uint8 occupying a single byte. If the string contains non-ascii characters, each character in the string is a Uint16, occupying two bytes. To determine which type of string we're dealing with, we store a negative length for Uint16 arrays and a positive length for Uint8 arrays. The length always refers to the array length and therefore the number of characters, rather than the number of bytes.

Strings layout:

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|             Length: Int32                 | (If length is negative, the string is a Uint16 array.)
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|               Hash: Uint32                |
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|   Data: Uint8[](Length)|Uint16[](Length)  |
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Because they have dynamic lengths, strings are always stored by reference.