The ISAAC cipher: Difference between revisions

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We choose the translate the Pascal version as the it’s easier to translate to Nim from Pascal rather than from C.

This is not an exact ~~transation~~: the more important difference is the use of a global state record rather than a list of global variables. This global state is transmitted to each procedure. This way, it is possible to run several PRNG concurrently.

This is not an exact translation: the more important difference is the use of a global state record rather than a list of global variables. This global state is transmitted to each procedure. This way, it is possible to run several PRNG concurrently.

We ~~have~~ also replaced the eight variables "a" to "h" with an array. This allows to simplify the code at several places by using a loop. And we changed the "mod" to "and", even if the compiler will likely optimize the modulo when the second operand is a power of two.

We also replaced the eight variables "a" to "h" with an array. This allows to simplify the code at several places by using a loop. And we changed the "mod" to "and", even if the compiler will likely optimize the modulo when the second operand is a power of two.

Note that the "mix" procedure could possibly be transformed in a template or be marked as "inline" (in the C version, it is a "define"). But as we are not in procedure whose performance is critical, expanding the code rather than calling a procedure is not very useful.

Note that the "mix" procedure could possibly be transformed in a template or be marked as "inline" (in the C version, it is a "define"). But as we are not in a procedure whose performance is critical, expanding the code rather than calling a procedure is not very useful.

<syntaxhighlight lang="nim">import strutils