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dtoa.h
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27 
28 #ifndef V8_DTOA_H_
29 #define V8_DTOA_H_
30 
31 namespace v8 {
32 namespace internal {
33 
34 enum DtoaMode {
35  // Return the shortest correct representation.
36  // For example the output of 0.299999999999999988897 is (the less accurate but
37  // correct) 0.3.
39  // Return a fixed number of digits after the decimal point.
40  // For instance fixed(0.1, 4) becomes 0.1000
41  // If the input number is big, the output will be big.
43  // Return a fixed number of digits, no matter what the exponent is.
45 };
46 
47 // The maximal length of digits a double can have in base 10.
48 // Note that DoubleToAscii null-terminates its input. So the given buffer should
49 // be at least kBase10MaximalLength + 1 characters long.
50 const int kBase10MaximalLength = 17;
51 
52 // Converts the given double 'v' to ASCII.
53 // The result should be interpreted as buffer * 10^(point-length).
54 //
55 // The output depends on the given mode:
56 // - SHORTEST: produce the least amount of digits for which the internal
57 // identity requirement is still satisfied. If the digits are printed
58 // (together with the correct exponent) then reading this number will give
59 // 'v' again. The buffer will choose the representation that is closest to
60 // 'v'. If there are two at the same distance, than the one farther away
61 // from 0 is chosen (halfway cases - ending with 5 - are rounded up).
62 // In this mode the 'requested_digits' parameter is ignored.
63 // - FIXED: produces digits necessary to print a given number with
64 // 'requested_digits' digits after the decimal point. The produced digits
65 // might be too short in which case the caller has to fill the gaps with '0's.
66 // Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
67 // Halfway cases are rounded towards +/-Infinity (away from 0). The call
68 // toFixed(0.15, 2) thus returns buffer="2", point=0.
69 // The returned buffer may contain digits that would be truncated from the
70 // shortest representation of the input.
71 // - PRECISION: produces 'requested_digits' where the first digit is not '0'.
72 // Even though the length of produced digits usually equals
73 // 'requested_digits', the function is allowed to return fewer digits, in
74 // which case the caller has to fill the missing digits with '0's.
75 // Halfway cases are again rounded away from 0.
76 // 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
77 // and a terminating null-character. In SHORTEST-mode it expects a buffer of
78 // at least kBase10MaximalLength + 1. Otherwise, the size of the output is
79 // limited to requested_digits digits plus the null terminator.
80 void DoubleToAscii(double v, DtoaMode mode, int requested_digits,
81  Vector<char> buffer, int* sign, int* length, int* point);
82 
83 } } // namespace v8::internal
84 
85 #endif // V8_DTOA_H_
enable upcoming ES6 features enable harmony block scoping enable harmony enable harmony proxies enable harmony generators enable harmony numeric enable harmony string enable harmony math functions harmony_scoping harmony_symbols harmony_collections harmony_iteration harmony_strings harmony_scoping harmony_maths tracks arrays with only smi values Optimize object Array DOM strings and string pretenure call new trace pretenuring decisions of HAllocate instructions track fields with only smi values track fields with heap values track_fields track_fields Enables optimizations which favor memory size over execution speed use string slices optimization filter maximum number of GVN fix point iterations use function inlining use allocation folding eliminate write barriers targeting allocations in optimized code maximum source size in bytes considered for a single inlining maximum cumulative number of AST nodes considered for inlining crankshaft harvests type feedback from stub cache trace check elimination phase hydrogen tracing filter trace hydrogen to given file name trace inlining decisions trace store elimination trace all use positions trace global value numbering trace hydrogen escape analysis trace the tracking of allocation sites trace map generalization environment for every instruction deoptimize every n garbage collections put a break point before deoptimizing deoptimize uncommon cases use on stack replacement trace array bounds check elimination perform array index dehoisting use load elimination use store elimination use constant folding eliminate unreachable code number of stress runs when picking a function to watch for shared function not JSFunction itself flushes the cache of optimized code for closures on every GC functions with arguments object maximum number of escape analysis fix point iterations allow uint32 values on optimize frames if they are used only in safe operations track concurrent recompilation artificial compilation delay in ms concurrent on stack replacement do not emit check maps for constant values that have a leaf deoptimize the optimized code if the layout of the maps changes number of stack frames inspected by the profiler percentage of ICs that must have type info to allow optimization extra verbose compilation tracing generate extra emit comments in code disassembly enable use of SSE3 instructions if available enable use of CMOV instruction if available enable use of VFP3 instructions if available enable use of NEON instructions if enable use of SDIV and UDIV instructions if enable loading bit constant by means of movw movt instruction enable unaligned accesses for enable use of d16 d31 registers on ARM this requires VFP3 force all emitted branches to be in long mode(MIPS only)") DEFINE_string(expose_natives_as
void DoubleToAscii(double v, DtoaMode mode, int requested_digits, Vector< char > buffer, int *sign, int *length, int *point)
Definition: dtoa.cc:56
const int kBase10MaximalLength
Definition: dtoa.h:50