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Fixed-width strings: Difference between revisions
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→Concatenation, substrings, and flattening
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The above example would create a deep tree, which is also undesirable. Therefore, a String instance contains a <tt>treeDepth</tt> field that contains the deepest depth of both subtrees plus one. The concat operation will contain a threshold where a string will be flattened before it is used for concatenation. This value should be determined using various benchmarks for optimal memory/performance ration. Also, the field is limited in size (10 bits?), so at some point automatic flattening is forced. | The above example would create a deep tree, which is also undesirable. Therefore, a String instance contains a <tt>treeDepth</tt> field that contains the deepest depth of both subtrees plus one. The concat operation will contain a threshold where a string will be flattened before it is used for concatenation. This value should be determined using various benchmarks for optimal memory/performance ration. Also, the field is limited in size (10 bits?), so at some point automatic flattening is forced. | ||
''In SM, buffer allocations are not exact, but on certain | ''In SM, buffer allocations are not exact, but on certain boundaries (16 bytes?), leaving spare room at the end, so appends are possible. When appended, a new String instance is created that shares its buffer with the original instance, just longer. This technique would inhibit the use of 0x00 string terminators.'' | ||
Getting a substring also flattens the source string. The substring is an instance that contains a pointer to the source string, and pointer to the start of the source string buffer. The length field contains the string length. This string is already flat, although it contains a reference to another string. It may be desirable to have a separate flattening function for this case. | Getting a substring also flattens the source string. The substring is an instance that contains a pointer to the source string, and pointer to the start of the source string buffer. The length field contains the string length. This string is already flat, although it contains a reference to another string. It may be desirable to have a separate flattening function for this case. | ||