Actions
Bug #9847
closed
Cannot create new String when using File.read(size, buffer)
Description
This bug was first noticed in version 1.9.2 and is still present in 2.1.2p95
The attached script does the following to highlight this bug:
- create a file of 13 fixed-length records of a specific size: all records contain a repeated letter, A for the first, B for the second, through M
- Test
#1: read all records from the file and store them into an array of Strings, usingFile.read(size)and storing via 'cache << buffer' - Test
#2: read all records from the file and store them into an Array of Strings, usingFile.read(size, buffer)and storing via 'cache << String.new(buffer)'; buffer will be reused during each read, cache will hold copies - test cycle is run using a record length of 23 and a record length of 24, highlighting Ruby's optimization of short strings
Results of running this script:
- with a record size of 23, Tests
#1show the cache containing all records:[ A, B, ... M ] - with a record size of 24, Test
#1shows the cache containing all records:[ A, B, ... M ] - with a record size of 24, Test
#2shows the cache containing:[ M, M, ... M ]
Diagnosis & Notes:
- with a record size > 23 and reading a file using
File.read(size, buffer), buffer is in such a state as to prevent a new unique String from being derived - variations of this script showed that
String.newwas a creating new String object on each record read, but the contents of all of the Strings stored in the cache Array were being overwritten on each call toFile.read - this shows that
String.new(buffer)is creating new String objects, but that the underlying values of all strings based on buffer were sharing the same internal memory - this behavior exists in the "long string" variation of String; short optimized Strings do not share this property
Files
Updated by 
Updated by 
Updated by 
Updated by
Actions
Like0
Like0Like0Like0Like0Like0Like0