📄 rcs.ps
字号:
1157(script)S1409(would)S1689(take)S1885(much)S2137(longer)S2422(to)S2530(compute,)S2929(and)S3103(would)S3383(not)S3541(be)S3665(signi\256cantly)S4190(shorter.)S1836 V970(Using)S1259(deltas)S1542(is)S1659(a)S1753(classical)S2141(space-time)S2623(tradeo)S2872 H (f)show 10 -.5 mul h (f)show10 R2933(:)S3011(deltas)S3294(reduce)S3609(the)S3782(space)S4054(consumed,)S4535(but)S4714(increase)S2016 V720(access)S1012(time.)S1283(However,)S1711(a)S1793(version)S2124(control)S2444(tool)S2637(should)S2941(impose)S3267(as)S3387(little)S3608(delay)S3861(as)S3981(possible)S4346(on)S4483(programmers.)S2196 V720(Excessive)S1163(delays)S1462(discourage)S1938(the)S2104(use)S2281(of)S2408(version)S2746(controls,)S3137(or)S3264(induce)S3574(programmers)S4150(to)S4273(take)S4484(shortcuts)S4890(that)S2376 V720(compromise)S1252(system)S1568(integrity.)S2000(To)S2149(gain)S2359(reasonably)S2829(fast)S3011(access)S3303(time)S3518(for)S3671(both)S3886(editing)S4201(and)S4382(compiling,)S4850(RCS)S2556 V720(arranges)S1096(deltas)S1368(in)S1485(the)S1646(following)S2074(way.)S2334(The)S2528(most)S2762(recent)S3044(revision)S3406(on)S3546(the)S3708(trunk)S3959(is)S4066(stored)S4350(intact.)S4667(All)S4835(other)S2736 V720(revisions)S1117(on)S1253(the)S1411(trunk)S1658(are)S1815(stored)S2095(as)S2214(reverse)S2537(deltas.)S2861(A)S2969(reverse)S3292(delta)S3522(describes)S3928(how)S4135(to)S4248(go)S4383(backward)S4805(in)S4918(the)S2916 V720(development)S1277(history:)S1624(it)S1721(produces)S2122(the)S2285(desired)S2615(revision)S2979(if)S3082(applied)S3418(to)S3538(the)S3702(successor)S4126(of)S4251(that)S4443(revision.)S4862(This)S3096 V720(implementation)S1379(has)S1543(the)S1696(advantage)S2131(that)S2311(extraction)S2740(of)S2853(the)S3005(latest)S3246(revision)S3598(is)S3695(a)S3769(simple)S4066(and)S4240(fast)S4414(copy)S4638(operation.)S3276 V720(Adding)S1051(a)S1126(new)S1324(revision)S1678(to)S1788(the)S1942(trunk)S2185(is)S2284(also)S2477(fast:)S10 I2681(ci)S10 R2785(simply)S3090(adds)S3305(the)S3459(new)S3657(revision)S4011(intact,)S4290(replaces)S4648(the)S4802(previ-)S3456 V720(ous)S895(revision)S1253(with)S1467(a)S1546(reverse)S1868(delta,)S2122(and)S2301(keeps)S2563(the)S2720(rest)S2899(of)S3017(the)S3174(old)S3337(deltas.)S3660(Thus,)S10 I3920(ci)S10 R4027(requires)S4383(the)S4540(computation)S3636 V720(of)S833(only)S1041(one)S1215(new)S1411(delta.)S3852 V970(Branches)S1373(need)S1593(special)S1902(treatment.)S2366(The)S2553(naive)S2801(solution)S3156(would)S3439(be)S3566(to)S3677(store)S3904(complete)S4303(copies)S4591(for)S4740(the)S4895(tips)S4032 V720(of)S836(all)S969(branches.)S1411(Clearly,)S1762(this)S1939(approach)S2336(would)S2618(cost)S2811(too)S2971(much)S3225(space.)S3533(Instead,)S3878(RCS)S4100(uses)S10 I4304(forward)S10 R4659(deltas)S4924(for)S4212 V720(branches.)S1163(Regenerating)S1729(a)S1807(revision)S2163(on)S2297(a)S2375(side)S2570(branch)S2875(proceeds)S3263(as)S3380(follows.)S3769(First,)S4012(extract)S4317(the)S4473(latest)S4718(revision)S4392 V720(on)S864(the)S1030(trunk;)S1313(secondly,)S1737(apply)S2003(reverse)S2334(deltas)S2611(until)S2839(the)S3005(fork)S3215(revision)S3581(for)S3741(the)S3907(branch)S4222(is)S4333(obtained;)S4748(thirdly,)S4572 V720(apply)S974(forward)S1321(deltas)S1586(until)S1802(the)S1956(desired)S2277(branch)S2581(revision)S2936(is)S3036(reached.)S3433(Figure)S3727(5)S3810(illustrates)S4232(a)S4309(tree)S4491(with)S4702(one)S4879(side)S4752 V720(branch.)S1076(Triangles)S1483(pointing)S1847(to)S1955(the)S2107(left)S2270(and)S2444(right)S2663(represent)S3058(reverse)S3375(and)S3549(forward)S3894(deltas,)S4182(respectively.)S5130 V8 R2273(1.1)S5114 V2463 H2463 4932 lc2463 4932 mc2463 H2160 5114 lc2160 5114 mc2160 H2463 5296 lc2463 5296 mc5295 V2463 H2463 5113 lc2463 5113 mc5114 V2463 H2766 5114 lc2766 5114 mc5129 V2705 H2765 5114 lc2765 5114 mc5099 V2705 H2765 5114 lc2765 5114 mc5130 V2880(1.2)S5114 V3069 H3069 4932 lc3069 4932 mc3069 H2766 5114 lc2766 5114 mc2766 H3069 5296 lc3069 5296 mc5295 V3069 H3069 5113 lc3069 5113 mc5114 V3069 H3372 5114 lc3372 5114 mc5129 V3312 H3372 5114 lc3372 5114 mc5099 V3312 H3372 5114 lc3372 5114 mc5130 V3486(1.3)S5114 V3675 H3675 4932 lc3675 4932 mc3675 H3372 5114 lc3372 5114 mc3372 H3675 5296 lc3675 5296 mc5295 V3675 H3675 5113 lc3675 5113 mc5114 V3675 H3978 5114 lc3978 5114 mc5129 V3918 H3978 5114 lc3978 5114 mc5099 V3918 H3978 5114 lc3978 5114 mc5130 V4092(2.1)S5114 V4281 H4281 4932 lc4281 4932 mc4281 H3978 5114 lc3978 5114 mc3978 H4281 5296 lc4281 5296 mc5295 V4281 H4281 5113 lc4281 5113 mc5114 V4281 H4584 5114 lc4584 5114 mc5129 V4524 H4584 5114 lc4584 5114 mc5099 V4524 H4584 5114 lc4584 5114 mc5130 V4762(2.2)S5265 V4584 H4584 4962 lc4584 4962 mc4584 H5039 4962 lc5039 4962 mc5040 H5040 5265 lc5040 5265 mc5040 H4585 5265 lc4585 5265 mc5796 V4008(1.3.1.1)S5780 V4281 H3978 5962 lc3978 5962 mc5963 V3978 H3978 5600 lc3978 5600 mc5598 V3978 H4281 5780 lc4281 5780 mc5295 V3675 H3978 5780 lc3978 5780 mc5737 V3934 H3978 5780 lc3978 5780 mc5721 V3960 H3979 5780 lc3979 5780 mc4281 H4584 5780 lc4584 5780 mc5796 V4524 H4584 5781 lc4584 5781 mc5765 V4524 H4584 5780 lc4584 5780 mc5796 V4614(1.3.1.2)S5780 V4888 H4585 5962 lc4585 5962 mc5963 V4584 H4584 5600 lc4584 5600 mc5598 V4584 H4887 5780 lc4887 5780 mc6143 V10 R1699(Figure)S1990(5.)S2125(A)S2227(revision)S2579(tree)S2758(with)S2966(reverse)S3283(and)S3457(forward)S3802(deltas.)S6359 V970(Although)S1382(implementing)S1972(fast)S2150(check-out)S2577(for)S2727(the)S2884(latest)S3130(trunk)S3376(revision,)S3758(this)S3938(arrangement)S4471(has)S4639(the)S4796(disad-)S6539 V720(vantage)S1071(that)S1262(generation)S1724(of)S1848(other)S2093(revisions)S2494(takes)S2739(time)S2957(proportional)S3491(to)S3609(the)S3771(number)S4116(of)S4239(deltas)S4512(applied.)S4901(For)S6719 V720(example,)S1121(regenerating)S1657(the)S1817(branch)S2126(tip)S2270(in)S2386(Figure)S2685(5)S2773(requires)S3132(application)S3614(of)S3735(\256ve)S3923(deltas)S4195(\(including)S4645(the)S4806(initial)S6899 V720(one\).)S983(Since)S1236(usage)S1494(statistics)S1870(show)S2112(that)S2293(the)S2446(latest)S2688(trunk)S2930(revision)S3282(is)S3379(the)S3531(one)S3705(that)S3885(is)S3982(retrieved)S4366(in)S4474(95)S4604(per)S4761(cent)S4957(of)S7079 V720(all)S859(cases)S1108(\(see)S1307(the)S1468(section)S1790(on)S1929(usage)S2195(statistics\),)S2638(biasing)S2967(check-out)S3400(time)S3618(in)S3736(favor)S3986(of)S4109(that)S4299(revision)S4661(results)S4962(in)S7259 V720(signi\256cant)S1186(savings.)S1590(However,)S2029(careful)S2354(implementation)S3030(of)S3161(the)S3331(delta)S3573(application)S4065(process)S4412(is)S4527(necessary)S4962(to)S7920 VEP%%Page: 8 9BP/slant 0 def/height 1.000000 def10 R10 R40 V0(-)S580 V2792(- 8 -)S900 V720(provide)S1055(low)S1235(retrieval)S1597(overhead)S1992(for)S2138(other)S2373(revisions,)S2789(in)S2897(particular)S3309(for)S3455(branch)S3756(tips.)S1116 V970(There)S1233(are)S1386(several)S1700(techniques)S2159(for)S2307(delta)S2533(application.)S3064(The)S3251(naive)S3499(one)S3675(is)S3774(to)S3884(pass)S4088(each)S4302(delta)S4528(to)S4638(a)S4714(general-)S1296 V720(purpose)S1077(text)S1267(editor.)S1595(A)S1707(prototype)S2130(of)S2253(RCS)S2483(invoked)S2845(the)S3007(UNIX)S3296(editor)S10 I3569(ed)S10 R3703(both)S3921(for)S4077(applying)S4467(deltas)S4740(and)S4924(for)S1476 V720(expanding)S1172(the)S1330(identi\256cation)S1894(markers.)S2306(Although)S2720(easy)S2934(to)S3049(implement,)S3539(performance)S4079(was)S4271(poor,)S4516(owing)S4803(to)S4918(the)S1656 V720(high)S934(start-up)S1275(costs)S1511(and)S1691(excess)S1987(generality)S2422(of)S10 I2541(ed)S10 R2635(.)S2726(An)S2884(intermediate)S3419(version)S3749(of)S3867(RCS)S4092(used)S4310(a)S4389(special-purpose,)S1836 V720(stream-oriented)S1376(editor.)S1694(This)S1902(technique)S2320(reduced)S2665(the)S2817(cost)S3008(of)S3121(applying)S3501(a)S3575(delta)S3800(to)S3909(the)S4062(cost)S4254(of)S4368(checking)S4759(out)S4918(the)S2016 V720(latest)S965(trunk)S1210(revision.)S1621(The)S1810(reason)S2104(for)S2254(this)S2433(behavior)S2816(is)S2917(that)S3101(each)S3316(delta)S3543(application)S4020(involves)S4392(a)S4469(complete)S4868(pass)S2196 V720(over)S927(the)S1079(preceding)S1502(revision.)S2412 V970(However,)S1395(there)S1629(is)S1731(a)S1810(much)S2068(better)S2331(algorithm.)S2811(Note)S3041(that)S3227(the)S3385(deltas)S3654(are)S3811(line)S3997(oriented)S4360(and)S4540(that)S4726(most)S4957(of)S2592 V720(the)S884(work)S1131(of)S1256(a)S1342(stream)S1650(editor)S1925(involves)S2306(copying)S2670(unchanged)S3143(lines)S3373(from)S3608(one)S3793(revision)S4156(to)S4275(the)S4438(next.)S4706(A)S4819(faster)S2772 V720(algorithm)S1141(avoids)S1434(unnecessary)S1953(copying)S2307(of)S2423(character)S2820(strings)S3120(by)S3253(using)S3503(a)S10 I3580(piece)S3823(table)S10 R4023(.)S4111(A)S4216(piece)S4459(table)S4686(is)S4786(a)S4863(one-)S2952 V720(dimensional)S1245(array,)S1509(specifying)S1960(how)S2167(a)S2246(given)S2503(revision)S2860(is)S2962(`pieced)S3290(together')S3685(from)S3914(lines)S4138(in)S4251(the)S4408(RCS)S4633(\256le.)S4851(Sup-)S3132 V720(pose)S935(piece)S1177(table)S10 I1403(PT)S3182 V1520(r)S3132 V10 R1591(represents)S2027(revision)S10 I2381(r)S10 R2420(.)S2507(Then)S10 I2744(PT)S3182 V2861(r)S3132 V2900([i])S10 R3038(contains)S3403(the)S3557(starting)S3889(position)S4244(of)S4359(line)S10 I4541(i)S10 R4602(of)S4718(revision)S3312 V10 I720(r)S10 R759(.)S848(Application)S1354(of)S1471(the)S1627(next)S1833(delta)S2061(transforms)S2522(piece)S2766(table)S10 I2994(PT)S3362 V3111(r)S3312 V10 R3184(into)S10 I3374(PT)S3362 V3491(r+1)S3312 V10 R3648(.)S3737(For)S3910(instance,)S4296(a)S4374(delete)S4646(command)S3492 V720(removes)S1093(a)S1173(series)S1436(of)S1555(entries)S1857(from)S2087(the)S2245(piece)S2491(table.)S2776(An)S2934(insertion)S3320(command)S3750(inserts)S4047(new)S4249(entries,)S4576(moving)S4918(the)S3672 V720(entries)S1019(following)S1441(the)S1596(insertion)S1979(point)S2218(further)S2522(down)S2777(the)S2932(array.)S3224(The)S3411(inserted)S3759(entries)S4057(point)S4295(to)S4405(the)S4559(text)S4741(lines)S4962(in)S3852 V720(the)S874(delta.)S1155(Thus,)S1412(no)S1544(I/O)S1709(is)S1808(involved)S2190(except)S2483(for)S2632(reading)S2964(the)S3119(delta)S3346(itself.)S3634(When)S3905(all)S4038(deltas)S4304(have)S4525(been)S4746(applied)S4032 V720(to)S834(the)S992(piece)S1238(table,)S1493(a)S1573(sequential)S2014(pass)S2222(through)S2569(the)S2726(table)S2955(looks)S3207(up)S3342(each)S3559(line)S3744(in)S3857(the)S4014(RCS)S4239(\256le)S4402(and)S4581(copies)S4871(it)S4962(to)S4212 V720(the)S872(output)S1158(\256le,)S1341(updating)S1721(identi\256cation)S2279(markers)S2630(at)S2732(the)S2884(same)S3119(time.)S3382(Of)S3517(course,)S3832(the)S3984(RCS)S4204(\256le)S4362(must)S4588(permit)S4880(ran-)S4392 V720(dom)S930(access,)S1241(si⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -