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generalize padding funcs

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Motiejus Jakštys 2022-02-19 21:23:33 +02:00 committed by Motiejus Jakštys
parent 2fc925923f
commit ae2d3d5443
3 changed files with 20 additions and 19 deletions
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33
src/padding.zig
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@ -2,28 +2,29 @@ const std = @import("std");
// rounds up a u12 to the nearest factor of 4 and returns the difference
// (padding)
pub fn roundUp4Padding(comptime T: type, n: T) T {
return roundUp4(T, n) - n;
pub fn roundUpPadding(comptime T: type, comptime nbits: u8, n: T) T {
return roundUp(T, nbits, n) - n;
}
// rounds up a u12 to the nearest factor of 4.
pub fn roundUp4(comptime T: type, n: T) T {
return ((n + 3) & ~@as(T, 3));
pub fn roundUp(comptime T: type, comptime nbits: u8, n: T) T {
const factor = comptime (1 << nbits) - 1;
return ((n + factor) & ~@as(T, factor));
}
const testing = std.testing;
test "padding" {
try testing.expectEqual(roundUp4Padding(u12, 0), 0);
try testing.expectEqual(roundUp4Padding(u12, 1), 3);
try testing.expectEqual(roundUp4Padding(u12, 2), 2);
try testing.expectEqual(roundUp4Padding(u12, 3), 1);
try testing.expectEqual(roundUp4Padding(u12, 4), 0);
try testing.expectEqual(roundUp4Padding(u12, 40), 0);
try testing.expectEqual(roundUp4Padding(u12, 41), 3);
try testing.expectEqual(roundUp4Padding(u12, 42), 2);
try testing.expectEqual(roundUp4Padding(u12, 43), 1);
try testing.expectEqual(roundUp4Padding(u12, 44), 0);
try testing.expectEqual(roundUp4Padding(u12, 4091), 1);
try testing.expectEqual(roundUp4Padding(u12, 4092), 0);
try testing.expectEqual(roundUpPadding(u12, 2, 0), 0);
try testing.expectEqual(roundUpPadding(u12, 2, 1), 3);
try testing.expectEqual(roundUpPadding(u12, 2, 2), 2);
try testing.expectEqual(roundUpPadding(u12, 2, 3), 1);
try testing.expectEqual(roundUpPadding(u12, 2, 4), 0);
try testing.expectEqual(roundUpPadding(u12, 2, 40), 0);
try testing.expectEqual(roundUpPadding(u12, 2, 41), 3);
try testing.expectEqual(roundUpPadding(u12, 2, 42), 2);
try testing.expectEqual(roundUpPadding(u12, 2, 43), 1);
try testing.expectEqual(roundUpPadding(u12, 2, 44), 0);
try testing.expectEqual(roundUpPadding(u12, 2, 4091), 1);
try testing.expectEqual(roundUpPadding(u12, 2, 4092), 0);
}

4
src/shell.zig
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@ -71,7 +71,7 @@ pub const ShellWriter = struct {
});
fullOffset += len;
const padding = pad.roundUp4Padding(u12, fullOffset);
const padding = pad.roundUpPadding(u12, 2, fullOffset);
fullOffset += padding;
//const stderr = std.io.getStdErr().writer();
//stderr.print("\n", .{}) catch unreachable;
@ -209,7 +209,7 @@ test "basic shellpopcon" {
try testing.expectEqual(sections.getIndex(nobody), null);
try testing.expectEqual(
sections.sectionBlob().len,
pad.roundUp4(u12, bash.len) + pad.roundUp4(u12, zsh.len) + pad.roundUp4(u12, long.len),
pad.roundUp(u12, 2, bash.len) + pad.roundUp(u12, 2, zsh.len) + pad.roundUp(u12, 2, long.len),
);
const shellReader = ShellReader.init(

2
src/user.zig
View File

@ -74,7 +74,7 @@ pub const UserWriter = struct {
try self.appendTo.appendSlice(user.shell);
}
const padding = pad.roundUp4Padding(u64, self.appendTo.items.len);
const padding = pad.roundUpPadding(u64, 2, self.appendTo.items.len);
try self.appendTo.appendNTimes(0, padding);
}
};