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diff --git a/174/index.md b/174/index.md new file mode 100644 index 0000000..7e7e5c0 --- /dev/null +++ b/174/index.md @@ -0,0 +1,44 @@ +Title: Use fixed width integers for CSS length type +Author: rodarima +Created: Sat, 25 May 2024 23:10:31 +0000 +State: closed + +The current type for a CSS "length" like `80px` or `20%` is represented internally as a single `int` type, which doesn't have a fixed length. In C and C++, there is only a guarantee that an int will hold at least 16 bits, but the current assumption is that it will hold at least 32 bits. +``` +| <------ integer value ------> | + ++---+ - - - +---+---+- - - - - -+---+---+---+---+ +| integer part | type | ++---+ - - - +---+---+- - - - - -+---+---+---+---+ +| integer part | decimal fraction | type | ++---+ - - - +---+---+- - - - - -+---+---+---+---+ + n-1 15 14 3 2 1 0 + +| <------ fixed point value ------> | +``` + +Furthermore, as we introduce more length types we are going to run out of length bits for the value itself. A simple option could be to define the length as something like this: + +```c +typedef struct CssLength { + CssLengthType type; + union { + int i; + float f; + }; +} CssLength; +``` + +Which will duplicate the size required to store lengths to 64 bits, as the type will likely use 32 bits with padding and another 32 bits for the integer/float value (on 64 bits machines). It has the benefit that on 16 bits machines, the size will halve to 32 bits, as all members will reduce their size. + +--%-- +From: kalvdans +Date: Wed, 12 Jun 2024 20:44:41 +0000 + +As a first step maybe use `int32_t` for the type to make sure we get 32 bits even on 16-bit platforms? + +--%-- +From: rodarima +Date: Sat, 05 Oct 2024 17:28:01 +0000 + +Merged in #264
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