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adds +cue comments per review

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This commit is contained in:
Joe Bryan 2019-05-13 15:51:59 -07:00
parent 7c4b1bf105
commit 9e9b5b45c1
1 changed files with 39 additions and 9 deletions
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48
pkg/urbit/jets/e/cue.c
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@ -3,6 +3,19 @@
*/
#include "all.h"
#define CUE_ROOT 0
#define CUE_HEAD 1
#define CUE_TAIL 2
// stack frame for record head vs tail iteration
//
// In Hoon, this structure would be as follows:
//
// $% [%root ~]
// [%head cell-cursor=@]
// [%tail cell-cursor=@ hed-width=@ hed-value=@]
// ==
//
typedef struct cueframe
{
c3_y tag_y;
@ -47,15 +60,12 @@ _cue_pop(c3_ys mov, c3_ys off)
return *fam_u;
}
#define CUE_ROOT 0
#define CUE_HEAD 1
#define CUE_TAIL 2
u3_noun
u3qe_cue(u3_atom a)
{
// initialize signed stack offsets (relative to north/south road)
//
c3_ys mov, off;
{
c3_y wis_y = c3_wiseof(cueframe);
c3_o nor_o = u3a_is_north(u3R);
@ -63,17 +73,27 @@ u3qe_cue(u3_atom a)
off = ( c3y == nor_o ? 0 : -wis_y );
}
// initialize a hash table for dereference backrefs
//
u3p(u3h_root) har_p = u3h_new();
// stash the current stack post
//
u3p(cueframe) cap_p = u3R->cap_p;
// push the (only) ROOT stack frame (our termination condition)
//
_cue_push(mov, off, CUE_ROOT, 0, 0, 0);
// initialize cursor to bit-position 0
//
u3_atom cur = 0;
// the bitwidth and produce from reading at cursor
//
u3_atom wid, pro;
// read from atom at at cursor
// read from atom at cursor
// push on to the stack and continue (cell-head recursion)
// or set .wid and .pro and goto give
// TRANSFER .cur
@ -83,7 +103,7 @@ u3qe_cue(u3_atom a)
//
c3_y tag_y = u3qc_cut(0, cur, 1, a);
// low bit unset, cursor points to an atom
// low bit unset, (1 + cur) points to an atom
//
if ( 0 == tag_y ) {
u3_noun bur;
@ -109,7 +129,7 @@ u3qe_cue(u3_atom a)
u3z(x);
}
// next bit set, cursor points to a backreference
// next bit set, (2 + cur) points to a backref
//
if ( 1 == tag_y ) {
u3_noun bur;
@ -131,7 +151,7 @@ u3qe_cue(u3_atom a)
goto give;
}
// next bit unset, cursor points to a cell
// next bit unset, (2 + cur) points to the head of a cell
//
{
_cue_push(mov, off, CUE_HEAD, cur, 0, 0);
@ -145,6 +165,7 @@ u3qe_cue(u3_atom a)
// push on to the stack and goto pass (cell-tail recursion)
// or pop the stack and continue (goto give)
// TRANSFER .wid, .pro, and contents of .fam_u
// NOTE: .cur is in scope, but we have already lost our reference to it
//
give: {
cueframe fam_u = _cue_pop(mov, off);
@ -154,10 +175,15 @@ u3qe_cue(u3_atom a)
c3_assert(0);
}
// fam_u is our stack root, we're done
//
case CUE_ROOT: {
break;
}
// .wid and .pro are the head of the cell at fam_u.cur,
// save them on the stack, set the cursor to the tail and rad
//
case CUE_HEAD: {
_cue_push(mov, off, CUE_TAIL, fam_u.cur, wid, pro);
@ -165,6 +191,10 @@ u3qe_cue(u3_atom a)
goto pass;
}
// .wid and .pro are the tail of the cell at fam_u.cur,
// cons up the cell (and memoize), calculate its total width,
// and "give" the new value
//
case CUE_TAIL: {
pro = u3nc(fam_u.hed, pro);
u3h_put(har_p, fam_u.cur, u3k(pro));