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authorRoberto Ierusalimschy <roberto@inf.puc-rio.br>2023-11-03 15:26:13 -0300
committerRoberto Ierusalimschy <roberto@inf.puc-rio.br>2023-11-03 15:26:13 -0300
commit08a077d673b25cf1fbfe21794f240f4ff4999667 (patch)
tree77ae945c9a2680af23d5fa11c156482b35c14e04 /ltable.h
parent43c8e5bded052801f54a7439d18933b83570eb82 (diff)
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Full implementation of new representation for arrays
Diffstat (limited to 'ltable.h')
-rw-r--r--ltable.h63
1 files changed, 50 insertions, 13 deletions
diff --git a/ltable.h b/ltable.h
index 371e721d..b401aba1 100644
--- a/ltable.h
+++ b/ltable.h
@@ -51,31 +51,68 @@
51*/ 51*/
52 52
53 53
54struct ArrayCell { 54/*
55 lu_byte tt; 55** The array part of a table is represented by an array of cells.
56** Each cell is composed of (NM + 1) elements, and each element has the
57** type 'ArrayCell'. In each cell, only one element has the variant
58** 'tag', while the other NM elements have the variant 'value'. The
59** array in the 'tag' element holds the tags of the other elements in
60** that cell.
61*/
62#define NM ((unsigned int)sizeof(Value))
63
64union ArrayCell {
65 unsigned char tag[NM];
56 Value value; 66 Value value;
57}; 67};
58 68
59 69
60/* fast access to components of array values */ 70/*
61#define getArrTag(t,k) (&(t)->array[k - 1].tt) 71** 'NMTag' defines which cell element has the tags; that could be any
62#define getArrVal(t,k) (&(t)->array[k - 1].value) 72** value between 0 (tags come before all values) and NM (tags come after
73** all values).
74*/
75#define NMTag 0
63 76
64#define tagisempty(tag) (novariant(tag) == LUA_TNIL)
65 77
78/*
79** Computes the concrete index that holds the tag of abstract index 'i'
80*/
81#define TagIndex(i) (((i)/NM * (NM + 1u)) + NMTag)
66 82
67#define farr2val(h,k,tag,res) \ 83/*
68 ((res)->tt_ = tag, (res)->value_ = *getArrVal(h,k)) 84** Computes the concrete index that holds the value of abstract index 'i'
85*/
86#define ValueIndex(i) ((i) + (((i) + (NM - NMTag))/NM))
69 87
70#define fval2arr(h,k,tag,val) \
71 (*tag = (val)->tt_, *getArrVal(h,k) = (val)->value_)
72 88
89/* Computes the address of the tag for the abstract index 'k' */
90#define getArrTag(t,k) (&(t)->array[TagIndex(k)].tag[(k)%NM])
73 91
74#define obj2arr(h,k,val) \ 92/* Computes the address of the value for the abstract index 'k' */
75 (*getArrTag(h,k) = (val)->tt_, *getArrVal(h,k) = (val)->value_) 93#define getArrVal(t,k) (&(t)->array[ValueIndex(k)].value)
76 94
95
96/*
97** Move TValues to/from arrays, using Lua indices
98*/
77#define arr2obj(h,k,val) \ 99#define arr2obj(h,k,val) \
78 ((val)->tt_ = *getArrTag(h,k), (val)->value_ = *getArrVal(h,k)) 100 ((val)->tt_ = *getArrTag(h,(k)-1u), (val)->value_ = *getArrVal(h,(k)-1u))
101
102#define obj2arr(h,k,val) \
103 (*getArrTag(h,(k)-1u) = (val)->tt_, *getArrVal(h,(k)-1u) = (val)->value_)
104
105
106/*
107** Often, we need to check the tag of a value before moving it. These
108** macros also move TValues to/from arrays, but receive the precomputed
109** tag value or address as an extra argument.
110*/
111#define farr2val(h,k,tag,res) \
112 ((res)->tt_ = tag, (res)->value_ = *getArrVal(h,(k)-1u))
113
114#define fval2arr(h,k,tag,val) \
115 (*tag = (val)->tt_, *getArrVal(h,(k)-1u) = (val)->value_)
79 116
80 117
81LUAI_FUNC int luaH_getshortstr (Table *t, TString *key, TValue *res); 118LUAI_FUNC int luaH_getshortstr (Table *t, TString *key, TValue *res);