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https://bugzilla.tianocore.org/show_bug.cgi?id=798
SafeIntLib provides helper functions to prevent integer overflow
during type conversion, addition, subtraction, and multiplication.
Conversion Functions
====================
* Converting from a signed type to an unsigned type of the same
size, or vice-versa.
* Converting to a smaller type that could possibly overflow.
* Converting from a signed type to a larger unsigned type.
Unsigned Addition, Subtraction, Multiplication
===============================================
* Unsigned integer math functions protect from overflow and
underflow (in case of subtraction).
Signed Addition, Subtraction, Multiplication
============================================
* Strongly consider using unsigned numbers.
* Signed numbers are often used where unsigned numbers should
be used. For example file sizes and array indices should always
be unsigned. Subtracting a larger positive signed number from a
smaller positive signed number with SafeInt32Sub() will succeed,
producing a negative number, that then must not be used as an
array index (but can occasionally be used as a pointer index.)
Similarly for adding a larger magnitude negative number to a
smaller magnitude positive number.
* SafeIntLib does not protect you from such errors. It tells you
if your integer operations overflowed, not if you are doing the
right thing with your non-overflowed integers.
* Likewise you can overflow a buffer with a non-overflowed
unsigned index.
Based on content from the following branch/commits:
https://github.com/Microsoft/MS_UEFI/tree/share/MsCapsuleSupport
https://github.com/Microsoft/MS_UEFI/commit/21ef3a321c907b40fa93797619c9f6c686dd92e0
https://github.com/Microsoft/MS_UEFI/commit/ca516b1a61315c2d823f453e12d2135098f53d61
https://github.com/Microsoft/MS_UEFI/commit/33bab4031a417d7d5a7d356c15a14c2e60302b2d
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Sean Brogan <sean.brogan@microsoft.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
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